Don't audition for a job if you aren't interested in taking the role if you get it!

I just finished working on a low pay non-union theater gig, and I had a number of drop-outs after we cast. One person was union and didn't want to get a waiver, one person couldn't commit to the rehearsal dates and another was already booked on a gig.
Low to no paying gigs are still professional undertakings, because you are a professional actor, right?
Let's use the theater gig I mentioned above-
It is a professional showcase festival for emerging MFA playwrights; a low paying with 2-3 weeks rehearsal commitment.
The pay isn't going to be what you do this project for.
What makes this project something to take seriously is the networking opportunities: The upcoming playwrights, the established directors, the professors (with their resume and contacts), even making contact with me, the Casting Director. Make a good impression with any and all of the above will create working relationships that could lead to more work. Work begets work in this business. Keep this in mind-  Just because a casting director or director is currently working on a small project when you meet them, does not mean they don't work for bigger theaters or projects.
But if you drop out, flake out on rehearsal, or generally don't respect the project; a bad impression is a hard thing to undo.
Bottom line- Don't audition for a job you don't want to take, commit to and do your best in.