You mentioned going to dollar
coins. We use machines with two hoppers and vend both dollar
coins and quarters. Dollar bill gives quarters, 5 & 10 dollar bills give combinations of dollar
coin and quarters. For example a $5 bill gets you 3 gold dollars and 8 quarters.
Then we value the dollar
coin in the self serve bay at $1.25 so the customer gets a bonus for using it at the wash. Everyone else was priced at $1.75 for a cycle and we increased to $2 a cycle when we made this change. Customers mention it all the time and always favorable. So I am certain I get return business. Of course you need machines with two hoppers to make it work.