AFC is a business. How many other business do you see lowering their prices just now? Their overheads aren't decreasing, and tickets have been frozen for a couple of years. In fact, season tickets at Aberdeen are cheaper than a lot of other teams like Killie and Caley...and look at the bottom 6 fare they serve up.
Personally, I think having a special offer for existing season ticket holders is good. How many times do we hear complaints about how season ticket holders get no perks (cheaper tickets for cup games, etc)? Here it is.