I didn't make a big deal of it, because we had already spent three hours hanging out, smoking out, and fooling around with mutual oral. But it was a downer, because $500 for a mutual oral experience is not what I wanted. $300 I woulda been fine with, but $500 I felt a little disappointed.
She did the solid thing and gave me a makeup session a week later (she just her period the day after our session), after she went to the drugstore and got some condoms.
So to answer your question...it's fine, but it depends on what I'm paying. For $500, it's not okay. For $300, it would be fine.
Or if it's a girl who sees you over and over again for almost nothing...well, you can't be a cheapskate and concentrate on the minutia. I had a provider get ill during a session post-dinner, and so we didn't do much. I was disappointed, but she has given me so many great sessions that I wasn't at all upset.