[jcparkyn]

That's a very specific form of "hiding information".

Hiding information about why or how much you want a good/service is absolutely not fraud, morally or legally (IANAL).

On the other hand, giving misleading info about something you're selling probably is.

[charcircuit]

If you want another example with the buyer withholding information then imagine a place where kids 5 or under get a discount. Someone brings their child who is 6, but is small for their age. An employee applies the discount thinking the child is 5 and the parent says nothing. Revealing someone's age is a privacy issue they may think to themselves.

[exo762]

This example is just a breach of explicit terms of the contract.