There really are not that many of the original 2011 ones . Many have been redeemed.
I think 5 BTC is reasonable for average condition, 6+ for great. I also have some for sale. I am considering ebay for one of them though prefer to sell here for btc.
Still bidding over $1400
http://www.ebay.com/itm/Casascius-Bitcoin-Minted-in-Sept-2011-Version-1-With-Error-/181115649401?pt=US_World_Coins&hash=item2a2b557d79
Sold at $850:
http://www.ebay.com/itm/Original-Casascius-Physical-Bitcoin-Series-1-Minted-in-December-2011-/181115773817?pt=US_World_Coins&hash=item2a2b576379
Sold at $1075
http://www.ebay.com/itm/Version-1-Casascius-Bitcoin-Minted-in-Dec-2011-/190818189201?pt=US_World_Coins&hash=item2c6da67f91