In this case the scarcity of the product compared to demand determines the price.
Elasticity determines how quickly/easily the change in demand/supply affects the price.
In this case, High demand, low supply, high elasticity and prices increase very quickly.
Look at basschat market place to see how quickly basses sell. The buyer determines the price there. If the seller doesn't drop low enough, there is no sale. The only difference with basschat marketplace is usually the bass player isn't selling basses to make a living and will hang onto their bass for months rather than sell it at a lower price (low elasticy)