Technically you could measure anything's value in Bitcoin. Typically it is up to the seller. If the seller is not offering to sell a good in Bitcoin, and are only offering it in Fiat, then you have to do the conversion.
If a vendor only lists the Bitcoin price for their goods, the value is determined by how much Bitcoin it'll take for them to part with their product.
It's just a matter of perspective.
What do you measure the value of your Fiat in? Or the value of Gold in? Bitcoin is the only measuring stick that is finite. You are asking a similar question to "If a meter is valued in centimeters, then is a meter valueless without centimeters to measure it?"
