Here are a few selected hemi valve covers. There are many other versions out there.
This is the big mama, very rare came only on 300s. ebaY starting price was $495/ set. Exact same cover without the dimples is the most common hemi cover available and they go for $50 - $100/set.
These are next on the desirable list for Chryslers. Industrial and Marine (not shown) covers have the dimples and are 'performance' covers. These go fro $80 - $150 per set.
Here are a couple or RedRam covers, one w/ the name and one w/o the name but with dimples. Both go for $100 - $150/set.
Rarest of all non-Chrysler covers are the Desoto covers. These go for $150 - $250/set.