I'm displaying products on a boosted rack, but I'm not getting extra XP or Coins. What's wrong?

The amount extra that you're going to get is already factored in the display menu. For example, if normally you get 100 XP from selling "x" item, the menu will write 130 XP. You won't see the original amount but you can compare the bonus by trying to display that product on a different, non-bonus rack.