To also add to my point a ten year old can only earn so much money, set him a goal which is doable, such as £100 and once he reaches it buy the computer, still learns the lesson, and dont stop paying him once he gets a PC, £5 to make a spreadsheet(budget for groceries) teaching him life skills with his gift turning it into a tool . Good on you for buying him a PC but don’t let an opportunity to grow his character go to waste.
Don’t be the brother who buys him football shoes but never goes to the games.