You are overvaluing your ideas and undervaluing your execution.
If someone can see you do something once and repeat it, it wasn’t that awesome to begin with, unfortunately.
“Secret books” aren’t unique. Woot did “bags of crap” a decade ago, TONS of people do grab bag type sales.
Makers markets aren’t unique. They are everywhere.
The good ones aren’t good because they are unique, they are good because they are well executed consistently. Do that.
It up to you to pay for services rendered in full.
Would having change make that easier? Yea, probably. But it sounds like you went with the cheapest service you could find, and the fact that it’s cash only alone should tip you off you aren’t getting premium service, so why you would expect anything but what you got is beyond me.
Ultimately its your job to pay your debts. If you needed change, you should have gotten that ahead of time, or clarified they would have change.
The fact that you then short-changed them becasue YOU didnt prepare is super lame. Id have take the 20 dollar lesson learned and not ripped off a small business who just cleaned my house.