Lisa del Giocondo, aka the woman depicted in the Mona Lisa, was the wife of a middle class Silk merchant - which indicates to me that art was affordable and somewhat easy to obtain.
How much would it have cost the average family for a portrait from the great artists we know of the time (Da Vinci)? How did this stack up to lesser known artists (Boltraffio)?
This thread discusses your question; note however that that the artists discussed are all 15th century and prices are liable to have varied somewhat. Note also that there's somewhat of a discrepancy between the prices I cite and the prices cited elsewhere in the thread; I think that is because the other prices refer to average paintings and the prices I was citing refer primarily to large-scale altarpieces that would've been more or less the priciest things around. http://www.reddit.com/r/AskHistorians/comments/26cgmj/in_renaissance_italy_how_much_would_it_have_cost/