To be clear, escrow services like escrow.com exist precisely for this purpose - to protect both buyer and seller in an expensive transaction, and they charge relatively modest fees. Buyer sends money to the escrow service, the service tells seller to send the equipment to buyer, and there’s an agreed-upon inspection period. If the buyer is satisfied, the service releases funds to seller. Otherwise, buyer sends equipment back to seller (at their own expense), and once seller confirms receipt, escrow service returns funds to buyer. There’s professional dispute resolution if things really go south, and it’s certainly still very useful to vet the counterparty before the transaction - but this is mostly a solved problem.