like a pig in a poke

To be like a pig in a poke means that something is offered in a manner which conceals its true nature or value. On farms that use pigs for meat, they put a pig in a poke concealing the fact they will be slaughtered there by acting as if it is no big deal. In the figurative sense, a pig in a poke means you are told to do something in such a way it seems appealing but in fact is nothing like what it is really for.