Dear Economist,

An offer recently came up for me to buy, for ₤50, a discount card that halves the bill at many London restaurants. Three friends agreed to contribute equally to the cost and go out to a favourite restaurant, knowing that we would save more than this.

I got the card and booked the restaurant. Everything went fine until the end of an excellent meal. We had saved ₤58. But the other three only grudgingly handed over their ₤12.50 to me.

They felt they had ended up just buying me a free card. I thought the expectation was that since I went to the trouble of setting it up, and they had saved money, they would thank me for my efforts.

Martin Haigh, London

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Dear Mr Haigh,

You have only yourself to blame both for being so vague about the terms of the deal and for being so niggardly when you divided the gains.

After they paid you for the meal and the card, each of your friends saved ₤2 and the trouble of booking a restaurant, while you saved ₤52, of which ₤50 went towards your discount card. It is true that that is a gain for all of you, but it is an uneven gain.

Experiments in economic psychology have shown that most people would rather have no deal at all than accept a tiny gain while watching a fat cat guzzle the cream. Had you been a stranger rather than a friend, your dining companions would have simply refused your outrageous demands.

You should have been both more specific and more generous.

Telling your friends you planned to charge them ₤50 just for booking a restaurant would at least have spared you all this embarrassing evening.

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