Optimus Prime

I wish it's okay to buy my son Optimus Prime transformer to, but it's not. It is expensive and I do not want to spend money for the toy that I know he would play for a few months then afterwards ignore it. I know what will happen if he can have it just like the rest of his toys. He plays the new toys today and tomorrow I can see it everywhere on the floor. he said he could open his piggy bank to buy Optimus Prime and I told him no. I bought him lots of transformer already and now they are everywhere and anywhere here in his room. It makes me mad, but he doesn't care he just want what he wants. But he cannot get it this time eventhough he wouldn't stop asking me.