For a criminal defense attorney defending drug offenses is one of the best paying
Not true. Most drug offenses that criminal defense attornies get are for petty possession, or small sale claims. In nearly all of these, the individuals don't have much money, and you can't charge too much for it anyway, unless it's a very rich person with a very large possession charge.
Defense attorneys usually make $10,000 to hundreds of thousands defending a client from a felony drug charge and they get paid win or lose. Federal cases usually pay more than state cases and you can do both.
I don't know where you are getting those facts from, but that is certainly not he case around here. If you have a felony drug possession charge, the lawyer would be lucky to get $2-4,000. Usually, they have to pay paralegals, secretaries, and court documents, so all and all after defending that one case, spending a few days working on it, they walk away with about $500, not really worth it in my opinion.
Not all civil cases work off of a contingency. And you choose which ones you get to represent. So if you get a case that you don't think you can win, then you don't take it and you don't miss out. If you take the case and don't win, it's your own fault. If one out of every five cases you win in civil cases, that means out of five cases you get like $100,000-$1 Mill. If you defend felony possession charges and you get what noumenon claims, then you would make $50,000 off the same five charges. Nearly half the payout.
Personally, for lawyers at least, I think the money is in business law. But that's me.
If you want to become a lawyer just for the money, don't do it. Three years of lawschool is murder, and if you are only sticking through it for a paycheck you won't make it. You actually have to be interested in the material and want to go to class every day, want to read the cases. Because if you don't, even if you get your JD, you'll get a massive case of depression and suicidal tendancies.