They would probably lose money if they charged $50/year. A lot of people do not seem to grasp all the overhead that goes into a MMO. There are bandwidth and server maintenance expenses that goes way beyond the cost of maintaining a regular multiplayer game. There are salaries for the employees who develop content(art dept, writers, voice actors, programmers, etc...) that are released via patches(in between expansions), support staff, both GM and telephone/email support.
The list goes on and on. You can't expect that just because Skyrim was $60, ESO should be as well. The only scummy deal was with Xbox One. WHile Playstation plus is not required to play on PS4, Xbox live IS required to play on the Xbox One. I could be wrong, but pretty sure I read somewhere that Zenimax petitioned MS to allow it to bypass XBL, but MS said no, so people can blame MS fo that one.
EDIT - I have no doubt as others have said, there will be bulk packages, but most likely not near $50