I do agree that having something so mission critical be managed by someone making practically nothing off of you is concerning, but I dont think that changes all that much at double their price. Either way the second something goes wrong, you leaving as a customer is much cheaper for them than it is for someone to spend any amount of time fixing your problem.

Unless you're markmonitor big then as far as I can tell the best bet is to just go off of general sentiment about domain providers. Or maybe have it through a cloud company if you're spending enough on other things to warrant proper tech support?