`But in any case we cannot take the poor beast into the Mines,' said Gandalf. `The road under the mountains is a dark road, and there are places narrow and steep which he cannot tread, even if we can.'Goats are notoriously sure-footed, and are more plausible (if ugly). It really isn't that hard to get one, and even if you don't... I'm not sure they're "worth it" anyway. Moria isn't so huge that they make a major difference in travel times, and because of the spawn densities, you're going to get knocked off a lot.
I have a goat, but I don't actually use it all that much. I do use the stable system a fair amount though (although I Alt-TAB away during the ride because it's rather unpleasant to watch). Those goats can get you from one place to another without any battles along the way, which makes it totally worth the silver.