"DID happen once - when we were first starting out and 'hurting for gigs' ... a certain organization told us if we played this one dance for free, we could "name our price" the next time - of course there was NO next time !!! ..."

That happens a lot. It's one of the oldest scams around. Free audition.
I've had a couple of checks from owners bounce, but took them to them and they paid for them, including return charges, and they apologized. Of course they didn't do it on purpose.
I've been on the other side of the situation too. Never had a check bounce, but was often on a very tight budget where a small miscalculation could be trouble.
Some years ago, a friend asked me to work a small club with him and I agreed.
We set up and before the first set was over a fight broke out. After everything settled down, we started playing again and a few minutes later another fight broke out.
I just stood up and started packing my gear. Without a word, my friend did the same. We loaded up and he went back inside to see if we could get paid. He was gone about 15 minutes, and I was getting out of the vehicle to go see if he needed help when he came back out and told me that the guy needed persuading but finally agreed to pay us for the full night. My friend had a couple of skinned knuckles.
So thankful I don't have to do those type of jobs anymore!
Early in my career, when the Union was strong, I had an owner break a contract. It was a 12 month contract that had six months left on it. I went to the Union and complained. They called the owner in and he told them I was always late showing up and that he thought I was on drugs.
They called ME in and I told them that was bullshit and that I would be contacting my attorney to pursue a defamation of character suit.
The Union rep said he'd get back with me. After about a week, I found another job, but it was only a two-week contract. The Union then decided that since I was only out of work for a week that they would make the original guy pay me for the week!
My attorney DID send a letter to the owner and I got a full written apology from him. I enclosed a copy of the letter with my letter of resignation from the Union. That was 40 years ago. The amount of money I've saved over the years, not paying dues and work fees, has been maybe a thousand times what I was out from losing that job!
Footnote: A few years later, after I opened my own club, that original owner came in one night. The place was totally full of people. He came up and acted like I was his best friend. I told him he would have to leave because I was over capacity and didn't want to get in trouble. AHH, that was satisfying!
As is probably true with a lot of us, I could write a book.