Every teenage does the same thing. Remember, this is also a way the rebellion teenagers try to challenge their parents, test boundaries. It's up to the parents to hold their fort. Every time this happens we would struggle with ourselves and with them. Don’t want to say NO outright, afraid hurt their feelings, or make them think we don't love them. Don't want to say YES too easily because we are not rich enough to throw money around, and don't want to spoil them.
So, we'll discuss why they need it, give them a chance to state their case. If it's reasonable we'll say yes. Otherwise we'll say no. If they fight back saying why other people's kids have so and so but not me? Then we'll say: we have different priorities. We don't buy fancy toys but we do more sports and travel......
Be firm but calm when talking to him.