I understand your frustation, but look at it in another way - there is no short cut in life. Looking at how much money they make is only going to fuel your frustation. So do not put your feet in their shoes - it will not fit - making money is only one fraction of this whole life....there are much more in life where you may be ahead of them. If you ask them I am pretty sure they want something that you have....only human nature. True story - I have a millionaire buddy who wishes he had PhD because he always wanted it but could not - I have another friend he makes a decent $$ but has a broken family.....being content and not complaining helps a lot.

Now you are so close to getting it done - just get it done. It is very important to finish what you have started - this is the identity of a real person - trust me - you will be a front runner later in life. If you quit now - you will quit again because you will find something better. So its better for you to replan your PhD and take the problem and turn it into a passion. Come on man - there are people who will kill to be in your situation so embrace it and move forward with it. Also if you find another hobby (photography, sports, music lesson) of sort that will ease your frustation.

I was in a similar situation for a long time - wanted to quit my studies and jump in the same boat as others but my hunch told me to continue a path that I was in - looking back perhaps this path has been the best for me - and I tell this to others.

Imagine people callin you "hey Doc" - that will be a nice feeling to have.....not everyone gets that honor - at that point you'll be glad that you've earned it man.......go for it man - DO NOT QUIT....... GET IT DONE.....make yourself proud. I hope I helped you here.