And never mind the price negotiations, would go something like this
Salesman -- "hello sir, I see you are intrested in our new door knocker down thingy"
Purchaser -- "yes, I am very intrested, how much are they"
Salesman --"oh you are very intrested, well I have a deal for you, they are normaly $150.00 each but if you buy 20 or more I will take 10% off and give you free delivery"
Purchaser -- "wow, that sounds like a great deal, can you deliver them tomorow?"
Salesman -- "no sorry we only deliver on thursdays"
Purchaser -- " well ok then I will just take them with me today, I have a truck"
Salesman -- "oh , ok but there is a 20% up charge if you pick them up at the factory"