Yeah, they're just about as common as gold OoT cartridges, if not more common.
I'd say the non-holo ones are probably almost as common as the regular gold ones.
Now, if we're talking about grey ones, that's where things get crazy. A grey MM cart would mean that that was one of the demo carts used in places like Walmart to promote the game's release. They also have ones for OoT, from my knowledge.