"Fresh Apples here! Only the best apples for 2 dollars!" "I would like 1000 apples, please." "Sir, I only have 600 apples in the shop. I can give you those now, and I'll ask the guy across the street if he has any." "How much will that cost?" "I think he's also selling them at 2 dollars each. Let me just look - oh, nope, he's seen us talking and changed his sign. Well. Have these 600 at the quoted price, and if you want more you'll have to pay the new price."