The parties may be willing to trust Vince since he is the Technical Contact for .ai domains, as shown in this IANA page.
The cost is 2% of the price (so add to the total) with a miminum of $100. Use the price of Bitcoin at coinmarketcap.com website.
To use this service the two parties should make an agreement that specifies
I will lookup the domain and verify the sellers email, then send email to both parties to confirm that they agree, then I will tell the buyer where to send the Bitcoin, and ask the seller where I should send the payment on to. After I get the the payment I will transfer the domain and then forward the Bitcoin onto the seller (less my fee).