Yes indeed! BA is being "conned" by suppliers!
Carriers in the US receive their amenity kits almost free of charge - all they pay for is the wash bag to wrap it all up in, the comb (if any), eye shades and socks! Why?
Because, on a European trip, if a traveller has used "Brand X" toothpaste or "Brand Y" shaving foam on his/her flight over, he/she will recognise it when they have to buy a tube in the local chemist!
I'm sure if our teams were to approach Colgate Palmolive etc in the right way, we'd obtain similar deals - instead BA prefers to go down the "designer" route!