I think it would depend on where it was, although I really have no clue.
For example, I would expect a video game store in the mall to have a much higher percentage of people not buying anything than an isolated / strip mall store due to the amount of foot traffic that would be entering out of sheer boredom or out of curiosity.
Storefronts in a mall come quite a bit closer to being good as a comparison for stores on the web.
I'm sure it's higher than 1-3%