You've already been accepted by this outfit and played a gig successfully. I don't think it would be errant to ask what the pay would be, I would sort of think they'd expect it. I probably would. Most pro musicians would want to know. You won't look like a jerk for asking. It should be a non-issue.
I have no problem with those who play for free. I mean, really, if you can afford to do it and you don't mind, it's really no big deal. You shouldn't be pigeonholed into playing for money just because of others who tell you "you have to get paid". I've done both; been paid for fill-ins and done free work. I don't mind the freebies, they're often fun and there's a low level of expectation. I feel that many artists, whether musical or otherwise, pursued their passion regardless of the financial gain.
Let's look at this realistically; if you are a pro and your livelihood comes from playing, you probably have the time, the chops, and the ability to command top money for what you do. If you are making a living off of music, then you must be (or should be) very good at what you do. Better than us weekend warriors. Those of us who play for free do it because it's not our livelihood. We have day jobs, some very good, and we do our music because we love it. That means that we can't, and don't, dedicate the time to what we are playing that you do. So you are usually better musicians. You should be, it's how you pay the bills. You can make the shows, make the practices, and work many hours a day at being the masters of your craft. Unpaid musicians cannot do this because they are working at some job that commands their attention. And you should have no qualm with those who play for free; we don't lower your value because you should be better. You typically are. It's really no different than any other skill or ability; if you are the best at what you do, you don't do it for free because you have time, investment, and skill. If you're "okay", you might not get money for it, or you might.
This is true of any profession. If you are good at what you do, have invested the time, have the skills, and you're in demand, you get paid (and often paid well) for it. If you're the best at what you do, you get more. But you don't get paid just because you CAN do something. You get paid when you do it well, or better than others can who do it for less or for free.
In the end, it's a personal decision. Think you're good enough to get paid? Ask for it. Insist on it. Doing it for fun and don't care about the money?.....then it's just a plus.....but don't gripe when you don't get paid.....you didn't ask for it and you may not have earned it....
For those of you good enough to make music a living....you have my utmost respect. You are better than me, you've invested the time, invested the effort, and I'm sure your abilities dwarf mine in comparison....so for that, I am in awe.
Ask about the pay. You won't look like a jerk.
