Lex was aware of the flaw of what he was doing. By putting items in the Gift shop, merely to read their descriptions, exposed them to being bought by others. That's exactly why, lately, when he put items in the shop, he would always make them ridiculously expensive, and slap some restrictions on them as well, for example, the buyer has to have Privilege tier 5.
When he put the Phantasm core within the Gift Shop, he similarly put countless restrictions on it, leaving it in the shop merely as long as it took for a description to be formed and for him to read it, before pulling it back.
