Edward, even if you are right (probably you are), there's always the alternative for the older trucks owners.
You can purchase "non original" Toyota parts for 10 - 30% of their official catalogue price.

I just checked the prices of some parts specified by Duodeluxe.
The wheel cylinder for Toyota 6, 4 tonner you may buy in TVH for 30-35 Euro (Toyota catalogue - about 300 Euro)
Brake booster - 230-250 Euro, Toyota price: ~ 1100 Euro.

I know that the genuine parts are usually better (not always), but for older trucks owners this is a reasonable alternative