E Jane Dickson: 'Look! The dragon's squeezing the lady so hard her swimming costume's come off'

The skateboards in Selfridges are mean machines, gorgeously decorated with writhing sci-fi creatures and pneumatic porno-gals. They are also, when I sneak a look at the price tags, 60 quid.

"I don't think these are what we're looking for," I tell Con, whose birthday money is burning a hole in his pocket.

"Aw, Mum, this one is perfect," he says, reverently stroking the overpriced plywood. "Look! The dragon's squeezing the lady so hard her swimming costume's come off!"

"No," I insist, flashing distress signals at the sales assistant who's hovering nearby, "it just isn't suitable."

The assistant, to his credit, sees my predicament, and adopts a man-to-man attitude with my excited seven-year-old. "These particular boards," he points out, "are more for professional or performance standard use."

"Yes," says Con, who has twice had a go on his friend Harry's board, "that's exactly what we're looking for."

"And," I chip in, "they're incredibly expensive." Con waves away this objection with his £20 note. "The money, Mum, is not important." It's a theme he develops with some passion while I tow him the length of Oxford Street to a bargain store where we find a skateboard (with snake, sans floozy) for a tenner.

It's high time, I humph to myself, that the children learnt The Value of Money. It's true that I have rather harped in the past on the "money's not important" angle, fearing the kind of creepy infant capitalist who calculates the interest on their Christmas money, but there has to be a happy medium. From now on, I announce, in return for making their beds and clearing the table, they will earn the princely sum of 20p per day to do what they like with.

Rather to my surprise, the children embrace the New Deal with enthusiasm. Clara has plans to "adopt" a disadvantaged goat in an animal refuge (a worthy cause I have cruelly refused to fork out for) and lays away her cash every night in the top drawer of her desk. Conor, for whom deferred gratification is a non-starter, blows the lot on a copy of The Beano after just three days.

It's all going terribly well, until I stop off in the chemist's after school to buy a new mascara. "And what," Clara wants to know, "have you done, Mummy, to earn this treat?"

"When you come to my age," I tell her, "make-up isn't a treat, it's a necessity."

Clara is unimpressed. "Goats have necessities too, you know," she says, drawing a concerned look from the chemist, "and I'm supposed to earn the money for that." I'm not inclined to explain the distinction, so I change tack. "I think I do my share of the chores at home," I tell her. "And besides, I earn my own living."

Clara sniffs. I can feel a Gordon Brown money-and-morality speech coming on, but I'm not in the mood to care. The capitalist world isn't fair. Goats - like the rich - are different.