No, my logic is fine, my analogy is flawed, cause there are no procs in RL, you should either nevermind that nuance or nevermind the P.S. completely.
I can actually fix the analogy: instead of material - give tailor money and ask him to buy material. You know what material costs and you give just enough money for 1 pair of pants, but what you don't know is that they have a SALE on material at 50% discount. So tailor uses half of your money to buy the material and keeps the other half of money for himself, not charging you any fee, of course.
So there, there ARE procs in RL, after all.