Do you only buy your children toys at christmas/birthdays? I often let them buy themselves something when we go shopping which I suppose is quite rare, but we fly once a month and they will pick up something at the airport. I remember my parents always saying no to me in shops, I suppose to teach me the value of money. It didn't work though as I am hopeless with money. I don't want my kids to be spoilt, but I also feel it's a bit unfair on them as they have parents who buy things without looking at the price-tags, so why shouldn't they be able to?
They don't have more toys than others, nor walk around in designer gear and still get very excited about getting a toy or present. But how strict should you be ?