I guess because the 522 is nothing more than two 510s in one box. Where as the 721 and the 921 are based on the same linux software and are more closely related. The 921 is nothing more than a 721 with double hard drive and it can do hd.
The 721 has more 'unrealized' potential than the 522 has of 'unrealized' potential. The 721 was supposed to have internet functions and other misc interactive things that it hasn't had yet and may never.
The only thing the 522 is supposed to have that the 721 was never to have is the capability of supporting dual/independant outputs so that it's dual tuners can be used seperately in two different rooms.
Currrently the 522's dual tuners operate much diffeferently than the 721's regardless of how Dish said they would work when it was released.
Maybe the core point is that the hardware needed for the possible future functions. So the 721 had more possible functitons than the 522 has. Thus different hardware, different software, both of which all costs more.
They probably won't ever charge on those receivers again ,but they were trying to charge for those origonal dishplayer dvrs recently. The price for those was like 9.00 a month. I don't know it they did charge for them but there were some threads on it a few months ago.
With Charlie you never know. I never would have thought that he would charge at all for the dvr functions. That was one of the great strengths of Dish over Tivo and cable , was that there were no fees on the dvr. Now there seems to be a fee for everything. Dish is sounding more and more like cable.
Hopefully Rupert will do away with the dvr fees at Directv which will force Charlie to do the same.