I think it's a pretty good explanation, as is garmonbozia's. But I'd add a couple of things. I agree with garmonbozia he's not so much a salesman but a peddler or hawker. In his left hand it looks like a small megaphone for calling out to people as they pass buy. He might have a horse or cart though not shown.
The Italian
bagatella means "a trifle." So he's someone of little standing and might be a bit shady. His merchandise is probably cheap and not very good. It's easy to see how this image would have evolved from the earlier magician images since no doubt he's familiar with the art of trickery.
Here's a link to a long paper on the etymology of
bagatella. Probably more than you'll ever want to know but has some good stuff.
El Bagatella.