hahaha!! Same thing here! I think that since it's 'his' toy really, he can do whatever he wants with it. Playdoh ends up getting gross after awhile anyway after being dropped on the floor.
So it's not like it lasts forever.
What about making your own then? It's much more cost effective. If you google it you can find countless recipes, it's soooo easy!
T's playdough is currently this gross yellowy brown colour from mixing yellow, brown, orange, white, and pink!