A basic cake of that time will cost £ at least in basic ingredients. When 250g butter is now £2.50, your probably looking at £7-10 for a large cake and covered in buttercream depending on size. Decent eggs, chocolate , flour, vanilla all need to be added ££. You can’t probably make a decent three layer cake for much change from £20 min
how long would it take you to make a basic yet decorated cake? I have no idea but at a guess 2 hrs min to make/ bake/ cool/ clean up. 2 hour to decorate. Even if a baker charges say £15 per hour for work, that’s £60 just on ‘time’ not actual ingredients.