So I started playing online roughly 3 weeks ago, right after R* patched the game for jobs to pay less, I've had 2 full weekends of play and otherwise I do work for a living so I've played a bit after work. Last night I reached level 64 and I wondered how much cash I've made so far as I seem to spend it as soon as I get it. A problem I have in real life too.
I've managed to amass 1.8 million dollars so far. I've never farmed for cash or levels either, I've strictly played what I feel like playing when I feel like playing it. I can also confirm that racing a fully modded vehicle in any class is a huge advantage over other vehicles.
Seeing as I wasn't farming I suspect 1.8 million isn't even that much for being level 64 but it's enough to afford pretty much anything in the game that I would have wanted. I even lost 200k of that 1.8 to the GTAO bug along with a car.
So there you have it. Do the jobs and activities in GTAO pay enough? I'd say they do if you just play the game.