Payment Gateway API and Webhook Costs
Where per-call pricing exists, webhook volume realities, and where this overlaps with API-gateway-cost (different category).
Major payment gateways (Stripe, PayPal, Braintree, Adyen, Square) do not charge per API call or per webhook delivery. The fee is per transaction. Where per-call pricing does exist is on adjacent services: Plaid charges per linked account (production pricing is quote-only via plaid.com/pricing), Stripe Radar charges 5c per fraud screen, Stripe Tax charges 0.5%, Stripe Issuing charges from $3 per US virtual card and $0.10 per active card per month plus interchange-style transaction fees (see stripe.com/issuing/pricing), and some niche payment-orchestration vendors (Spreedly, Primer) charge a per-transaction routing fee on top of the underlying processor.
Where per-call pricing exists
- Plaid Auth: per-item linked, production pricing quote-only (plaid.com/pricing). Plaid Identity, Transactions, Income all priced separately.
- Stripe Radar: 5c per screen on Standard, $0.05 + custom rules on Radar for Fraud Teams (stripe.com/radar/pricing).
- Stripe Tax: 0.5% of the transaction (capped per region) (stripe.com/tax/pricing).
- Stripe Issuing (US virtual cards): from $3 per card created, $0.10 per active card per month, plus per-transaction authorisation fees (stripe.com/issuing/pricing).
- Payment-orchestration vendors (Spreedly, Primer, Gr4vy): typically 5-15bps + per-tx fee on top of the processor.
Webhook reliability
- Stripe retries failed webhook deliveries with exponential backoff for up to 3 days, then marks events stale.
- PayPal retries IPN/webhook deliveries for up to 25 attempts over 15 hours.
- Adyen retries notifications for 8 days with exponential backoff.
- All gateways require an idempotent webhook handler. The volume of duplicates from retries is the practical reason.
Webhook volume reality
On a typical SaaS at $1M/yr ARR, expect 20-50 webhook events per paid customer per year (subscription created, renewed, payment succeeded, payment failed, refund issued, dispute opened, etc.). A 1,000-customer book generates 20K-50K webhooks/yr, which is well within the “free” webhook budget on every major gateway. The cost is not the call; it is the engineering time to handle them reliably.
Different category: API gateway cost
This is not the same as API gateway cost (AWS API Gateway, Cloudflare Workers, Kong) which charges per API call to your own services. See apigatewaycost.com for that category. Payment gateways and API gateways share a word but solve different problems.