This applies most to No1 son (aged 15) who is mad keen on cycling - he does jumps/stunts at skate parks. Each year, as we approach Christmas or his birthday he always has some expensive bike component that he desperately needs - mainly to upgrade the bike as the stuff he does on it means the bike needs to be bomb-proof. He has a paper round and often asks for a contribution from us, as his main present, towards whatever expensive bit/new bike he needs, making up the rest from his own money.
The other two boys do this to a certain extent too, and it finally got too much for me recently, and I read everyone the riot act about not wanting to be seen as simply the Bank of Mum and Dad, there to bankroll whatever they 'order' for Christmas/birthday.
I am probably being very unreasonable, as I do understand that if they are going to get a big gift for Christmas/birthday it should be something they really want, but I am starting to feel that I'm only here to do the paying, and that I put more thought into the gifts for my friends' children than I do for my own. It all seems rather cold and mercenary to me.