It's the same as exchange rates, constantly being recalculated. Though crypotcurrencies are orders of magnitude more volatile. A seller will set their price in USD (or other established fiat), and convert the price to bitcoin at the time of transaction.
As far as cryptocurrencies are concerned, I personally view BTC as a good store of value; it's slow and expensive to transfer compared to other coins.
As far as cryptocurrencies are concerned, I personally view BTC as a good store of value; it's slow and expensive to transfer compared to other coins.