I find that specific sounds can be tough, as they either have to be found or recorded, and from my own experience I find recording my sounds that I always get a hiss in the back of the dialogue that isn't quite drowned out by the standard background music.
Also, unlss you're using pre-exisiting sounds, like the wolf howl, you have to request the user to download them, which is usually a much larger file. For this reason alot of sound packs are optional downloads, but it does still add that bit of an extra server cost to the user.
Just my two cents on the topic, though.
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