Had this recently, bought a dehumidifier for a good price, marked as new - arrived and had obviously been opened and didn't work. Out of a desire to have a dehumidifier sooner than later I was about to open it up when I saw it already had been, so I opened a return instead and sent it back.

I can only assume it is worth it for the seller to sell untested goods as new, a good number must work long enough for the buyer to be happy.