According to another dictionary it's not necessarily about money:

https://www.merriam-webster.com/dictionary/scam


And it would be quite slippery if it was only about money - for example if Alice and Bob barter services and Bob fails to deliver I'd say it's still a scam even if money is not involved. Now if Alice provides a service and wants confidentiality in return (get your mind out of the gutter) then confidentiality must have value for Alice, and the service must have value for Bob, but it wouldn't be a scam if Bob didn't hold up his end of the deal?