I think they've been forced to follow the market there. In the early days they criticised this approach in interviews, and stuck to just two pricepoints ($5.99 and $9.99). As they've expanded, they've increased the range of pricepoints and now you have things like the Telltale Games adventures which have massive RRPs but are ~75-85% off in a sale http://www.gog.com/game/tales_of_monkey_island
