I went to a fast food restaurant and...

[mustang1]

When I got to the counter the guy asked if I wanted anything else with my sandwich. I said no and he asked (I am quoting verbatim):

"Would you like a free drink for £1.50?"

It still erks me that I didn't have a good response except "err, no thanks".

 

[screenman]

Bargain, you should have bought 2.

 

[Archie_tect]

I bought a sandwich in Morrisons yesterday for £1.99 and as I got to the counter the lady told me that I could get a free drink and a packet of crisps in their meal deal for £2.50, saving me £1.75....

 

[Oldbloke]

Not fast food but when I had a big shop at Asda, I paid £200 in cash, rest on card.

The girl then asked if I wanted Cashback.

 

[Sandra6]

On lesser folk these tactics work.
When I was about 7 I helped my dad run a charity tombola stall. He told me the tickets were 10p each, 3 for 50p. I started to correct his maths, but he gave me a wink and proceeded to sell tickets, all of them 3 for 50p.

 

[Markymark]

I was with a bunch of friends at a beach in Spain. Bit drunk we all decided we wanted a burger king so I volunteered. I went to the counter and ordered 20 whoppers and 20 large fries. She asked if I was eating in or taking away!