BitcoinWallet.com is a solid domain, and is bought with a purpose. All that results in a very high price.
The best .com domains related to Bitcoin are taken, but there might be a few that are still free to register.
It requires a lot searching for a solid .com domain, but that's the challenge. Find a good domain and you'll get good money for it.
Try to find domains with max two words in it, and I mean not something like BitcoinCool.com or GangsterBitcoin.com, etc.
Find something that a company or interested people can use as a service and such.
I think this is the best answer so far. I for one look for short, simple, and seo friendly domains.