You can't sell them on the normal commodities market if they are banned. Only the black market will buy them, but since you paid for them they aren't stolen so they don't lose half value. I was buying tobacco for 4500cr per unit, and the black market at the place that banned them was paying around 5600cr.
For the extra effort it takes to smuggle stuff in, there should be some kind of bonus on the sell price but it appears to just be normal supply and demand prices. Lol, be sure you really want to be a smuggler because if you get caught the fines are amusingly humongonormous. 200 units of contraband tobacco will get you a 1.5 million credit fine and instantly turn them from neutral to hostile. If you get that in the Federation, Empire or Alliance they'll be after your head in all those systems and you will have to grind lots of missions to get back to unfriendly rep. It's silly, you have to sneak into the station to pick up missions to do for them to get back to unfriendly so they don't kill you on sight.