body: If I enter an establishment that offers drinks/coffee/food and say "I'd like a coffee/beer/whatever" and the waiter gives it to me, shouldn't they explicitly mention that it's not for free?
  
  
  If some person is handling pens with ads on a corner, and I say "I'd like a pen" could the person just reply that it's $1?
  
  
  Would the scenarios above be any different if a mentally challenged person went through them?
  
  
  
title: Contract law: implicit payment?