Got a reference for that? I’ve read tons of Tolkien’s stuff surrounding the world building of Middle Earth, but I don’t recall the exchange of self for magic usage.
There isn’t one. In classic internet forum fashion sone makes something up, forgets it, half-remembers it and then promotes it as fact.
There’s a lot of lore regarding Tolkien’s world, I easily could have missed something. Many other universes that use magic definitely have a quid pro quo cost for that usage, and I wouldn’t be surprised if there were something in the LOTR universe that mentions it in passing. There’s quite a bit about Gandalf’s magic usage (or mostly lack thereof, for such an incredibly powerful character his usage is very sparing) and I’d be curious if there’s a canon writing from Tolkien that backs up the reasoning for that, like loss of life energy or whatever.
If there is, it’s not in The Hobbit or LotR itself. Silmarillion is impenetrable to me, so idk.
I honestly can’t recall. It’s been decades since I’ve read anything from Tolkien.