[Osiris]

Hi my shop that I usually use has ran out and won't be back in stock for another month, so I found c2bit/centralshop/cardhouse, they have 5000 uk cards available but I notice that someone is buying them the moment they are added (even though theres older ones available).
So 1) is it trusted? 2) Is there a reason why someone is buying out the newest but not the ones that are 2 weeks old?