The number of times people would need to change a ten into fives or ones would be a bit too rare for a dedicated machine. What you need is a machine on which you could select exactly what combination of bills and/or coins you want. This could actually work both ways. That is, you could also put ten dollars worth of coins and small bills in and it could give you a ten (or 2 fives or whatever).

The problem with a reverse machine is that it probably would prove too popular. Banks usually charge a fee for consolidating small coins into bills as small coins have a habit of building up in pockets and are hard to get rid of.

There is no profit in such a machine, unless the user has to slip a quarter in there as well.

I disagree - there are many times I would change a 10 for a five and five ones. Next to a vending machine, I would very readily sate my thirst for one of those dollars, where I could not with just my ten.

Int he case of ibeing associated along vending machince and such, yes it would be profitable for the vending machine owners. That is the same as a coin change machine at a laundromat or self car wash. But one standing alone is of no profit to anyone, unlessyou have to pay a small fee for the service.