Selling via Ebay could also be an option. AFAIK prices are often higher there.

Why would anyone buy a physical bitcoin in the first place?

To brag about to your friends --- be careful though, you might lose them, especially when prices follow the trajectory foretold by John McAfee
To make hodling easier (yes - I would probably have spent it if it weren't a physical bitcoin)
Because you don't have one
Because you want to show it to your grandchildren "granddad owns a Real Casascius Bitcoin!"
Because you are a coin collector

Any other reasons?