How do you scam a scammer?

I know it's probably not that easy but worth asking I guess.

I got scammed a few months ago, actually only for $85 worth of BTC for something I was going to buy (never received) but because of stupid practically invisible check boxes (which include all wallet sections) on the exchange that I didn't notice, I actually sent 0.021 BTC (about $650 USD at the time, more now).

Scammer claims that I need to pay the 'fees' of another $30 so they can send it back to me (I know). I've obviously got their wallet address. Just wondering how those dusting scams or things like that work... Maybe there's a way of tricking them into sending it back..

I imagine it's technically over my head but worth asking.