I dunno exactly, but my brother's girlfriend's father's boss's secretary's sister's next-door neighbors' priest's cousin's union shop steward's uncle's Knights Of Columbus club Sergeant-of-Arms's nephew's best friend did it real cheap for me once.
That depends on the speed of the change and the mass of the bulb. Or vice versa, of course. It just might be easier to leave the bulb and change the room. It's all relative.