It could be that Adobe is allowing for a reduced price for the current version, or maybe just supply and demand.
As to whether PrE 7 is "better" than PrE 8, that would probably be highly subjective and might vary user to user. Still, it does seem that more are having issues with PrE 8, than they did with PrE 7, at least by scanning the posts to this forum.
I paid less for PE7 than I did PE8. Bought it as a combo with photoshop. I paid $104 delivered (PE7 and photoshop in Jan 2010). Do a google search and you'll find a good price.