[charcircuit]

For example. Person A is selling a car that is severely cosmetically damaged. To get a better deal they hide the appearance of the car for privacy reasons. When the buyer finally gets the car they realize that they overpayed because they didn't know how bad it was.

This to me would be a case of fraud. Whether commiting fraud like this is illegal is a legal question.

[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.