I am an artist and some of my commissions do come from the Internet - collector sees my work, contacts me, we meet and I sell the piece or sign a commission contract.
However I do not sell any of my works directly over the web, I do not even offer this option on my site. Why?
There two reasons - one is that I believe that the collector should meet the artist in person or at least see the artwork of this artist in real-life before making the decision to purchase.
Second reason - to pay 4-5 digit figure over the net without seeing the actual artwork in real-life is a bit strange.

Yes, if you already collecting works of the particular artist or have seen the artwork you want to purchase in the museum or gallery therefor sure of what you are getting, then like anything else you may be able to find a better price or buying may be just more convenient over the net.

I hope this helps, let me know.

PS. While selecting the artist for your collection on the Internet and if considerable price is asked, look into artists bio - not for the titles but for persistency. You do not want to pay a lot of money and find out later that the artist became
a car salesman for example (no offense to car salesmen).

Ilia Anossov
http://www.truefresco.com/anossov
commission work
http://www.truefresco.com/ila

Whoever will se this post I might be wrong any other ideas?