charityselfer
A person who works behind the scenes in a thrift shop or charity outlet, who vets donations for self gain before the public. Or a person who is buying charity donations and purposely grabs a item that you picked up and put down as they think there's money to be made in it.
Excuse me can I squeeze in to take a look at those records? Yes but only when I've picked the best out, Jez you're acting like a real charityselfer!