[cjy]

I believe patio11's point is that the opportunity cost of a domain name is the same regardless of which currency you use to buy it. If you use Bitcoins, you have less Bitcoins. If you use dollars, you have less dollars to convert into Bitcoins if you think they will appreciate. Your net position in Bitcoins need not be affected by your choice of currency for this particular transaction.

[seliopou]

I think that's right. But then, if you don't want your bitcoin position to change, and you have no need for its other features in this transaction, then why use bitcoin? The OP's point stands.