Middle-run is not worth it, is to work only with high-level professionals. And better that the artist was distinctive, that his style must be guessed at once.
If you directly from the artist, then the price he appoints himself, and then you can bargain and come to the same amount, which satisfied both.
Although, it all depends on the artist, some are not traded.
In all the galleries in different ways, once listened to Aidan Salakhova, she said that the minimum price for the work of young artists - 2,500-5000 $, which is to begin. Otherwise there is no sense.
If you want the price rose, promotion of the artist to go to the gallery owner: exhibitions, catalogs, PR, etc. The only condition for the artist, it should be working, stagnation in the work are not welcome!