After a year of building in this space, I keep running into the same walls. Stripe rate-limits metering events at 100 req/s — a ceiling that's invisible until you hit 10M events/month, usually at the worst possible time.
Every major cloud billing platform charges a percentage of revenue that sounds fine at $1M ARR and becomes a $150k/year line item at $30M, for infrastructure whose actual cost to the vendor barely moved.
When pipelines misbehave, there's no audit trail you control — a Vercel customer got a $96k bill in a single month from a misconfigured deployment with nothing to catch it early. I tried to find a comparison of the main platforms that wasn't written with a vendor's thumb on the scale, couldn't, so I wrote one covering 7 of them.