Since when has game length ever equaled price, if that is true then pretty much every game out there should be no more than $10 - $20 really.
Well, keep in mind, RPGS are about developing your character over a long period of time, and TES is also about exploring a vast area. Action games (good action games in particular, like Half life or metal gear solid, not call of duty) are about quick and brutal combat. While you get less content per se, the developers spent far more time perfecting each inch of the game in an action game as opposed to an RPG, so its not fair to compare the two