I had a splendid breakfast at the bakery in The Royal William Yard on Sunday.
They do things a little differently there.
You help yourself to your breakfast & drinks and when it’s eaten, you tell the cashier what you ate and pay for it.
My order was:
1 croissant
1 black coffee
1 boiled egg.
But because I didn’t pay at that point, I also topped it up over a relaxed hour with the paper by having:
1 more black coffee
1 more egg.
Because my tab was open, it was easy to buy more.
I’m sure they have some people who do a runner without paying, but if the fine people extract a 70% upsell of most visitors, they will gain more than they lose.
Most importantly, their customers glow, they feel trusted and approved of. Sharers in the secret.
The Grinch Manifesto 
Those kind of dynamics are the sort of thing retail is very good at doing. I was reading about this recently and the way strategic decisions in supermarkets are made to up the average spend rather than make any individual spend much more as there is more to gain that way. Interesting stuff.
… And a great choice for a breakfast location :).