What farming covers here
Gold on your realm, profession materials by the stack, and hours booked for whatever you name. All three need live realms, so an order placed before launch is a reservation at the quoted price rather than a delivery, and the order page tells you the day work starts.
Fresh realm economics, and what they do to the price
In the first weeks there is almost nothing in circulation: materials sell for several times what they will be worth a month later, and gold is scarce because nobody has had time to farm any. That makes this the most valuable window to buy in and the most expensive one. The rate falls as the economy fills, and an order placed early keeps the figure it was quoted.