They're not necessarily demanding, it is all character and personality but what you have to expect and anticipate is that a bit of rebellion is entirely normal and should be embraced. Teens are finding their feet, assuming their true personality, assesssing what is importat to them and we have to stand back and let them find their own path, secure in the knowledge we have provided good foundations. Most will find their way through, some won't.
But costwise, oh yes it gets much harder and they need you more. In fact it always makes me smile when people despair about preschool childcare costs because childcare is far more complicated as children get older and you have to balance school/afterschool/before school/holiday childcare - up to 4 you only deal with one place! Also tweenie/teen holiday care is a nightmare as it is so often sports based clubs that run for shorter hours than other childcare providers.
But of course, you can only spend what you have and you have to be strict like that. If my children say they want something, we talk about costs in a realistic way (ie a laptop costs £500, Daddy brings home £1400 a month, we have to pay bills/buy food etc with that, do you see why that is a big expense?). Children need things being put into context. We always assess whether it really is essential and whether they can contibute themselves too. You have to teach budgeting and realistic expectations. I woudl never put up with my child demanding things, that is not the way we operate.
I mean, mobiles etc. Some teens ahve blackberrys, iphones and the like. For me that is a no. DH and I don't have expensive phones, so the teens don't need them either. If they saved up and bought one, fair play. I tell them I won't buy them as they become a target with a pricey phone.
But certainly clothes become pricier when you can no longer shop cheaply in supermarkets (the teen market is woefully lacking in clothes retailers), uniform at high shools costs, even our state school pe kit cost £100 and don't get me started on what the Grammar school pe kit has cost! Shoes cost more, and coats. School trips tend to be longer residential based, music lessons are pricier, trips out become cinema trips and skating type things rather than cheap walks to the park, their friends come from a broader areas meaning more travel, if they compete in sports they become county wide and you need the kits, the petrol to transport them...
BUT they are great - great to chat to, great debates, great to see the world through a younger more black and white person when our views become greyer as we get older. Teens have great passion and vision, great souls. They throw themselves into things wholeheartedly and believe anything is possible.