The margin for custom is worse than stock, but it's a sale with 0 over head (although you do need a high volume to even be able to do customs, but all of your dollars don't need to be in skates). Same with custom goalie; great for retailer but downside is you need to have a big stock in order to get volume in custom.
Ideally for the retailer they do not stock any skate above $600, and all high level skates are custom-only. The manufacture probably wouldn't like that though with a massive increase in labor costs.