I've been in a similar situation, probably not as extreme but nonetheless. Some things I would recommend you considering:

a) Consider the take-home after tax, and compare that as it does make the numbers a bit more realistic.

b) It's not just money, it's time and energy. If you're not entirely sold on the idea (which it sounds like you aren't), then it's probably going to be more enjoyable for you to continue your PhD.

c) Offers come and go, and you've got an idea of what's possible. Maybe you won't get the same again in the future, but maybe you'll find something mid-way post-PhD which will give you satisfaction of work and better pay.

Don't focus on the money, focus on the fact that you're going to be spending the majority of most days doing this thing, and do what matters to you.