even if its 80 for both - 80 dollars for hours upon hours of gameplay is totally worth it. but i'm biased - i love this game and have def gotten my moneys worth
If you have bottomless pockets, D3+ROS is a decent buy. I've gotten 600 hours out of it which I am generally satisified with.
If you have a tight budget and want to spend your money on a great game, I wouldn't choose D3
D3 is too easy to play. The initial stimulation wears off fast and as no thinking is required, it will become quite boring. There are many features of it which you will realise were put in to increase the longevity of the game. This may or may not bother you but you will notice it bothers many of us who've posted on forums.