I've spent a bit of money a few times, but in my opinion it was always worth it. I work a lot of hours (well over 40 most weeks, even though I'm salary), but I make good money, and I simply don't have the time to farm up a lot of credits. I also took a few months off for D3 (which was a huge dissapointment, but that's another matter) and when I came back I REALLY wanted the ex-cerberus vanguard... I regret nothing! It's my favorite class by far, and I'd even go so far to say as a little overpowered (I'm annihilating banshees in gold this weekend, helping pugs clear the objectives).
Most of the people who spend a good bit of real money on games are people like me who work a lot (and make good money, I'm doing quite well) but want to enjoy games as much as someone who gets to play a lot. If it means I pay for a dozen other people's DLC, so be it