You then also have issues of availability.
Me, I had to hunt down a non-insanely priced Millenium Falcon which still had all the cards. Took me a long old while, but got there in the end.
Yes there are advantages to that system, including distinct financial ones - but GW has done what GW has done, and it's turned out pretty well so far. Main bonus about GW stuff? Buy one book - all the stuff needed to play your army is in there. Sure there's additional spangles out there if you want them, but none of it is necessary to keep your hand in. X-Wing is a different story.