I have one. It was the cheapest one i could buy for $15 or something. Still working, best investment because it's beside my kitchen. It does not damage your door frame.
Mind you i purchased the cheapest, no gimmicks version.
Bought this one (not my pic) from Target for like $30. Doesn't damage the door/door frame. Maybe just some black scuff marks from the padding but that'll wipe off.