My dad works in the business, so I guess I've always known and taken it for granted.
Outside of Costa, almost everything he sells is Luxottica. It's a monopoly of the highest degree.
Also, Costa makes the best sunglasses. Those that think otherwise are wrong, frankly. Well, Maui Jims are pretty damn good too, so I guess that argument could be made. Other than those two though, it's a HUGE drop off.