It gets a little complicated. I am quoting from different redditors:
"Bitfinex has an open market allowing crypto to be loaned between its users. That loan can either be used to buy more crypto, or sold to profit on a crypto going down in price. The open market allows the rate to borrow to be set based on supply and demand.
A month ago, you could borrow Tethers for a rate of 6% per year, much more supply than demand. Now, that rate is closer to 30% as more people bet on Tether following in UST's footsteps. "
Response:
"That would mean that this tweet, sadly, is not the disaster that everyone is assuming it is. The 30% isn't something that's being paid by Tether that needs to print in order to get it to you, it's just the borrow cost of the short seller."
Explanation:
"One side’s APR is another’s APY since it’s P2P, so it encourages people to lend it out instead of cashing it out. It’s not bitfinex literally offering 35% to deposit your USD, but from the depositor’s standpoint it may as well be."
Thread:
old.reddit.com/r/Buttcoin/comments/upmgsw/30_interest_if_you_dont_withdraw_your_money_from/