rip-off /ˈrip ˌôf/ nounINFORMAL a fraud or swindle, especially something that is grossly overpriced. "designer label clothes are just expensive rip-offs" synonyms: fraud, cheat, deception, swindle, confidence trick; More an inferior imitation of something. "rip-offs of all the latest styles" so in this case the vitamins are either overpriced or do not contain what they say they do.

"Rip-off" is when a something is too expensive or something/someone is not legitimate (real). If you hear people saying that a person is a rip-off it means they are cheating you/someone else. If you hear people saying that a thing is a rip-off, it means the thing is fake. So, be careful!