I take on side work as a contractor where I bid on projects I'm interested in. Some of my clients are corporations or companies that I know have large budgets and are in it for the money; I have no guilt at charging what I think they're willing to pay (and I know they're still profiting off my work). One client pays me for a full-day even when I only work a few hours (which is like earning triple rate), and I'm like, f'yeah!
The problem I have is with indie clients and projects... the ones where someone is paying out of their own pocket, doing it for passion/art/creative fulfillment, a meaningful social cause, education purposes, etc. I'm not compromising my base rate, but I'm not charging double or triple when I could at times, or doing extra duties just for the sake of billing hours to clients who wouldn't care. I definitely find these projects fulfilling personally because I feel like I'm helping support their art or cause (most of the time the work I'm doing is pretty meaningless). But at the same time, I'm starting to get more clients who don't know the difference and are just coming in expecting to pay more. I don't know why I'm having trouble coming to terms with the fact that I should just take the money... that my guilt is costing me, not them.
I've talked to a couple colleagues about this, and they think I'm nuts. At the end of the day, it is about business, which I know! One colleague said, "if you don't charge it, someone else will." That still doesn't make it right to me, though.