The customer is always tight

There's a fairly common I find myself having with customers that can be paraphrased thusly:

Customer "I need this package to arrive as soon as possible in America or THE VERY WORLD WILL END!!!"

Me "We can guarantee it there in two days for £50"

C "That's too expensive. Have you anything cheaper?"

Me "We can send it in about 4 working days for £7.50"

C "That's still too pricey. What other services are there?"

Me "Normal airmail is £4.20"

C "Still too much."

Me "Surface mail is £2.50 but can take up to 2 months"

C "£2.50!?!?! Is there anything for less?"

Me "You can chuck it in the sea and hope it gets there for free."

C "Perfect."

Me "What about the world ending?"

C "Fuck it. I can't afford £2.50 to get this package halfway across the world."