Pick Polar if
indie / small product teams who will stay on Starter Free $0 (5% + 50¢, no Polar monthly fee) while they sell a first SKU, then buy Pro at $20/month when sales pass the ~$1,379/month breakeven and they want 3.8% + 40¢.
Read the Polar pagePick Unkey if
aPI teams who will stay on API Management Free $0 (150k valid requests, 1k keys, no card) while they issue a first keyspace, then buy Pro at $25/month when they need 250k requests and team workspaces — or start Deploy Starter at $5 when they also want the container host.
Read the Unkey page