I dont think they have the inventory advertised. Many times I'm waiting for a particular card, so checking multi times a day. Then I'll get an email that one is available and immediately login only to find no cards. It'll say "the last --- card sold 5 days ago"; so either the email or the site is wrong.
Other times I make an order, and then 6-7-8 days later (after the already advertised shipping period), the order will be cancelled for no given reason. Think they try bait and switch.