newegg's current hard drive specials are a great example of pricing and bang/buck...
You can get a 750GB western digital caviar black for under $79 now, which is a GREAT deal.
However...
You can also get a 1.5TB drive for $109, which is twice the storage for a lot less than twice the price.
What do you really need? For a primary drive if you don't have tons of data (videos, pics, etc), the WD drive is probably a better primary drive. It is fast and has a great warranty. But if you're a data packrat, that 1.5TB drive is amazingly good on storage/$ ratio.