Question for those of you who are artsy - what's your profit margin?

I was at an outdoor street arts festival this weekend in Alpharetta, GA (http://www.awesomealpharetta.com/pages/ContentPage.aspx?ContentName=Alpharetta_Streetfest) – this isn’t spam… the event is over.

I bought several framed photographs and some artist made glassware, at what I considered to be a fair price.

Out of curiosity, is there a way to know how much of this was profit? How much did the artist actually make over their expenses?

(Example: I bought a beautiful glass bowl for $200. The artist had to design it, make it, fire it, transport it, rent space at the art show, etc. Is it likely she made money on my purchase, or is this break-even? )