Couldn't agree more, our fans would be buying Belotti jersey from all over the world. Give him the number 7 shirt that his idol Sheva wore and watch the sales go through the roof!
Milan (and every other club in the world) makes a very "small" amount from jersey sales compared to the retail price of the jerseys. This is why Adidas pays Milan the yearly fee that they do. On top of what Milan makes from each jersey(I believe I saw a report a couple of years ago that clubs only make about 12 Euros per jersey sold on average), they also have to pay the player (let's say Belotti) if that player retained some/or all of his image rights (which is more than likely that he will).
So Adidas sold 200,000 Milan jerseys this year and Milan made about 2.5mil from those sales. How much do you think those sales will be boosted with Belotti?? Even if they are doubled, let's say even tripled (no way, but let's just go with it), that's still "only" an amount between 7 and 8mil Euros.