In this case it's probably not a fat-finger and more likely to be a software bug. The popular clients have warnings against against absurd fees, and even if you're crafting your own transactions (which might lead to absurdly high fees if you don't neglected to have "change" outputs), bitcoin core will check for this when you're trying to broadcast the transaction[1].

[1] https://developer.bitcoin.org/reference/rpc/sendrawtransacti...