Men's Health magazine says that the average cost of a four-month affair is $25,664.

"Before you take a long lunch with Sarah in sales, you might want to check with your accountant," the magazine said.

The magazine's list of expenses includes motel and hotel rooms, bar tabs and meals, roses, and gifts for a mistress.

But it also includes diamond earrings to keep a wife happy, money lost at work by not being focused and missing out on a promotion, and $5,000 in legal fees for a divorce, as well as money for a deposit on a new apartment.