I was with the Robert Klein Gallery in Boston from the early 90's to the late 90's. Probably sold about a dozen prints in that time. $600.00 for a no name photographer ( 1/2 to me ) is a lot of money for most collectors. I think most of my sales were to the coporate sector. Never had a problem getting paid with Klein.
Earlier this year I brought some work down to the 1st Street Gallery in Boca Raton FLA. http://www.1streetgallery.com/Index.aspx Beautiful space, loved my work, haven't sold a thing yet!
The real problem, at least for me is to print a portfolio worthy of showing to galleries takes about a year between traveling and other obligations time slips by.
I still have doubts about those reporting brisk sales via their web sites, alot of money for something sight unseen. Far too much time and effort go into my prints to sell for a few hundred dollars.
Without a doubt, I can say having sold photographs for twenty years that the most sales come from personal contact and a little self promotion