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Resonance uses Polar for billing and subscription management with a pay-as-you-go pricing model based on character usage.

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Pricing Model

Resonance charges based on the number of characters you convert to speech:

Pay as You Go

$0.30 per 1,000 charactersYou only pay for what you use. Characters are metered in real-time as you generate audio.

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What Counts as a Character?

  • Every character in your input text, including:
    • Letters (A-Z, a-z)
    • Numbers (0-9)
    • Punctuation (. , ! ? etc.)
    • Spaces and line breaks
    • Special characters
Character count is calculated from the exact text you submit for generation. Empty characters and formatting are included.

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Example Pricing

Text LengthCharactersCost
Short paragraph250$0.075
Blog post2,000$0.60
Article5,000 (max)$1.50
10 articles50,000$15.00

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Subscription Setup

1

View Subscription Status

In the sidebar footer, you’ll see:
  • “Pay as you go” card if you don’t have an active subscription
  • “Current usage” card if you have an active subscription
2

Start Subscription

Without a subscription, you cannot generate audio. Click Upgrade to begin.
3

Polar Checkout

You’ll be redirected to a secure Polar checkout page where you can:
  • Review pricing details
  • Enter payment information
  • Complete subscription setup
  • Set up billing details
4

Return to Resonance

After successful checkout, you’ll be redirected back to Resonance with an active subscription.
5

Start Generating

You can now generate audio! Usage will be metered and billed automatically.

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Usage Metering

Resonance uses Polar’s event-based metering system:

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How Metering Works

  1. Generation Request - You submit text for speech generation
  2. Character Count - System counts characters in your text
  3. Subscription Check - Validates you have an active subscription
  4. Audio Generation - Creates the audio file
  5. Usage Event - Sends metering event to Polar with character count
  6. Cost Calculation - Polar calculates cost based on characters
Metering happens asynchronously and doesn’t block your generation. Even if metering fails temporarily, your audio is still generated.

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Viewing Current Usage

The sidebar shows real-time usage estimation: 
Current usage
$2.47
Estimated this period
This displays:
  • Aggregated usage across all active subscriptions
  • Estimated cost for the current billing period
  • Updates as you generate more audio

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Understanding the Estimate

  • Usage is tracked across all organization members
  • Costs accumulate throughout your billing period
  • The estimate may have a slight delay (eventual consistency)
  • Final billing is always accurate based on recorded events

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Managing Your Subscription

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Access Customer Portal

1

Open Portal

In the sidebar footer, click Manage Subscription on the usage card.
2

Polar Customer Portal

You’ll be redirected to Polar’s customer portal in a new tab.
3

Portal Features

In the portal, you can:
  • View current subscription status
  • See detailed usage breakdown
  • Update payment methods
  • View billing history
  • Download invoices
  • Manage subscription settings
  • Cancel subscription

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Subscription Status

Your subscription can have several states:
  • You can generate audio freely
  • Usage is being metered
  • Sidebar shows current usage and cost estimate
  • Portal access is available
  • Cannot generate audio
  • Sidebar shows “Upgrade” button
  • Existing generations remain accessible
  • Custom voices are still available (for when you re-subscribe)
  • Polar will attempt to retry payment
  • You may temporarily lose generation access
  • Update payment method in customer portal
  • Contact support if issues persist

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Billing Cycle

Polar handles billing on a recurring basis:
  1. Billing Period - Typically monthly (check your portal for exact dates)
  2. Usage Accumulation - Characters metered throughout the period
  3. Invoice Generation - Polar creates an invoice at period end
  4. Payment Processing - Automatic charge to your payment method
  5. New Period - Usage resets and new period begins
You can view your exact billing cycle dates and next invoice date in the Polar customer portal.

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Organization-Level Billing

Important details about how billing works with organizations:
  • One subscription per organization - Not per user
  • Shared usage pool - All members contribute to the same usage total
  • Organization admin manages billing - Only admins can access checkout and portal
  • External customer ID - Polar uses your organization ID to track usage
If multiple organization members generate audio simultaneously, all usage counts toward the same organization subscription and bill.

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Cost Optimization Tips

Batch Your Content

Generate multiple related pieces in one session to streamline workflow and estimate costs accurately.

Optimize Text Length

Remove unnecessary whitespace, repeated content, or markup before generating to reduce character count.

Reuse Generations

Check generation history before creating new audio - you may have already generated similar content.

Monitor Usage

Regularly check the usage estimate in your sidebar to stay aware of costs throughout the billing period.

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Technical Implementation

For developers interested in how billing works:

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Subscription Check

Before every generation: 
const customerState = await polar.customers.getStateExternal({
  externalId: ctx.orgId,
});

const hasActiveSubscription = 
  (customerState.activeSubscriptions ?? []).length > 0;

if (!hasActiveSubscription) {
  throw new TRPCError({
    code: "FORBIDDEN",
    message: "SUBSCRIPTION_REQUIRED",
  });
}

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Usage Metering Event

After successful generation: 
polar.events.ingest({
  events: [
    {
      name: "tts_generation",
      externalCustomerId: ctx.orgId,
      metadata: { characters: input.text.length },
      timestamp: new Date(),
    },
  ],
});

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Cost Estimation

The sidebar calculates estimated cost: 
let estimatedCostCents = 0;
for (const sub of customerState.activeSubscriptions ?? []) {
  for (const meter of sub.meters ?? []) {
    estimatedCostCents += meter.amount ?? 0;
  }
}

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FAQ

  • You immediately lose access to generation features
  • All existing custom voices and generated audio remain accessible
  • You can view but not create new content
  • You can resubscribe at any time to resume generating
Yes! Use the Manage Subscription button to access the Polar customer portal where you can update your payment method at any time.
  • Polar will attempt to retry the payment automatically
  • You’ll receive email notifications about the issue
  • Update your payment method in the customer portal
  • If payment fails repeatedly, your subscription may be suspended
The estimate shown in your sidebar is very accurate but may have a slight delay due to event processing. Your final invoice is always calculated from the exact events recorded.
Refund policies are managed through Polar. Contact support through the customer portal to discuss refund requests.
No, this is not a credit system. You pay only for what you use each billing period. There’s no expiration or rollover because you’re not pre-purchasing characters.
Check your Polar product configuration. Typically, pay-as-you-go means you only pay for usage, but there may be a minimum subscription fee set in Polar.

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Support

For billing and subscription support:
  • General questions: Click Help and support in the sidebar
  • Payment issues: Access the Polar customer portal
  • Technical issues: Contact Resonance support team
  • Billing disputes: Reach out via the customer portal

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Next Steps

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