High cost of Campag & Shimano brake spares.

I cannot understand why one has to pay over £20 for brake blocks. When I first bought spares for my Weinman brakes I bought a card of red blocks for £3 the card held about 20 pairs. Now with my Campag Veloce I am expected to pay £22 & my Shimano 105 over £16. I actually currently use Fibrax blocks which permit repacing blocks into the shoes. Also I understand other makes with similar atributes are available. But the brake manufacturers seem to adhere to over inflated prices.