What you are suggesting is done though. Paid human drug trials are definitely a thing. I've considered doing them before since one of the bigger pharmaceutical testing companies are set up near where I live, actually, since they can pay well enough. I'm just too much of a pussy. I also was, for a short period of time when I was in school, approved to do experiments on human subjects. I was licensed for Psychological, but we had to study the medical end of it too before taking the test. (and don't worry, when I say 'short period of time', I mean that the licenses expire rather quickly and I haven't had any reason to renew it. I didn't kill anybody.)

When people talk about morality in human experimentation, they are talking about either the Mengele style vivisection (Which is seriously what I thought you were advocating), or faulty debriefing. Of course, they do preliminary tests to make sure there isn't a meaningful chance of fatality, but you'd want drugs tested thoroughly before put on the market anyway. The later aspect, faulty debriefing, is a matter of those doing the testing failing to tell the volunteer what they were getting into. This was the (first) problem in the Tuskegee experiments, they flat out lied about what they were doing. 

The other major issue I recall was that you have to be careful with rewards, because you don't want the reward to become a carrot-on-a-stick used as leverage rather than reward.

Following these regulations though, these things are perfectly legal and part of the process for bringing drugs onto the market. 

...and the good the Hitler experiments bring us is a hell of a controversy. Technically... a lot, but any time that information is used it causes some significant debates. Quite a bit of what we know about hypothermia comes from these experiments, though. And that's not counting the earlier experiments done on poor people and slaves in the nineteenth century. Vivisection produces results, this is true, but the evil that came with them was way worse.

...and when it comes to life insurance, the insurance company itself is a regulatory committee. The difference between a hospital practicing vivisection and an insurance company is that the vivisectionists want patients but can't get them honestly, whereas the insurance company doesn't want to pay out and will do what they can to make sure they don't give a pay out to murderous fraudsters.