I don't think it is just because of the venue. It does happen all the time unfortunately. Both Keith and I have experienced this time and time again. People want custom work done. You try to work up what they want. They either change it several times or adding things in. Some of the requests are impossible.
I had a customer have me work up a design that took over half a day to do (several hours) and then in the end he said "I showed it to my client and he changed his mind" and felt he didn't have to pay me. What about MY time and MY day lost? I think that was the straw that broke my back.
Now we tell people up front - we charge $25 an hour for custom work. That includes the consultation time and the 'tweaking' time. We have been doing this long enough to know an approximate amount of time it will take us to complete the design. We don't do anything until we get half down, unless we know the customer well. Usually the time involved is anywhere from 2-4 hours. That price tag is usually enough to deter people from wasting our time. If they agree to move ahead, we do. But most of the time we ask for half up front.
It may seem like a lot, but we are "Graphic Designers". It took us YEARS to learn our craft and we need to have that respected. Hiring a graphic designer usually begins at about $80 an hour and up, so they are getting us at a bargain.
The most difficult thing as a business is to respect yourself as a professional so others do as well. Loose and casual relationships with customers only come after much experience with them. New customers should be treated professionally and also with respect - be on time. Be honest. Do your best work.
While everyone will conduct their own business differently, as it suits them, this is what works well for us.
I wish you all the best.
Sheila