従量課金と使用量ベースの価格設定

Flat subscriptions do not fit products where cost scales with consumption — like AI tokens or API calls. Metered billing charges customers for actual usage, aligning revenue with cost.

Stripe prices come in two usage types:

• Licensed: a fixed quantity (e.g. 5 seats)
• Metered: quantity reported over time and billed at period end

Define a recurring price with usage_type: metered. Stripe sums reported usage for each billing cycle.

For metered items you do not set a quantity at subscription time — Stripe learns it from usage reports.

As customers consume the product, report usage against the subscription item. Use action: increment to add to the running total.

Report at the moment usage happens — for example, after each AI completion count its tokens. Buffer high-frequency events and flush periodically to avoid hitting API limits.

Avoid double-counting on retries by sending an idempotency key. Stripe ignores duplicate requests with the same key.

You can combine metering with tiers: the first 10,000 units cost more per unit, additional units less. Stripe computes the blended total automatically.

Customers want transparency. Fetch the current period's usage and display it in their dashboard so there are no billing surprises.

Many SaaS use a hybrid model: a fixed monthly base fee (licensed) plus metered overage. Add both prices as separate items on one subscription.

Run metered billing reliably:

• Use metered prices for consumption-based products
• Report usage with increment and idempotency keys
• Consider tiered pricing for volume
• Show usage to customers for transparency

You added usage-based billing:

• Create metered prices and subscribe without a quantity
• Report usage with increment and idempotency keys
• Use tiered pricing and hybrid base-plus-overage models
• Surface usage to customers for transparency

Your AI SaaS now charges fairly for what users consume.