Earlier quoted context omitted.
You can't really do better than stripe. The onboarding overhead is because of fraud and the costs are basically barely above interchange.
Stripe needs all that byzantine fraud prevention, on top of what they had a decade ago, because they are a huge concentrated target. A smaller firm could be way simpler. Because they simply wouldnt have enough money to provide a decent payday for dozens of malicious geniuses going at them 24/7/365.
You really don't have to be that big a payment processor for dozens of malicious geniuses to decide that they want to fleece you. If anything, the ROI is better in less sophisticated companies. Most ways to trick a payment company are, if anything, standardized. The smaller company can often be attacked by just changing the API calls, but otherwise taking basically the same actions you would to try to defraud a bigger fish.