There are substantially more people playing. Everyone also has the same idea at the beginning of ladder, "I'm going to farm my ass off, sell everything I find for as much fg as I can, then buy again later in the ladder for dirt cheap." If you expected prices to remain high, you underestimated the amount of people selling.
Also, I have no proof to back it up but they seem to have increased drop rates in D2R. I really don't put in all that much time, maybe a few hours per week, and the amount of HR/MR and elite uniques/sets has been nuts.