you can buy hacked accounts on the 360, basically loaded with millions of microsoft points, people buy those, then they buy packs on ultimate team and then transfer the players/coins generated to their real account through an auction or trade.
this then means that the 360 market is being manipulated into lower prices due to supply and demand, in a perfect world, both systems would have a difference but it would be little in it either way.
these special hacked accounts have a "slang name for them", i think they mostly come from china or something. they have basically stole someones account who has their credit card linked to the account and they buy all the points and change the gamertag and password, etc so the original owner cant get it back or its too late by the time they do get it back. i dont know how it works, im on the ps3 and never looked into much tbh.