I think you need to talk to the seller and be comfortable. It goes both ways. I bought two items recently. One expensive by your standards, one not that pricey. The expensive item involved some discussion and the seller shipped after I told him my payment was on the way. For the less expensive item, I told the seller I would purchase the item after I after I got home (1 week)from vacation. He received my payment by check and waited for it to clear, then shipped.
Both transactions involved a different level of trust. One for shipping early, and one for holdong an item that could have been sold sooner
In both cases I had good feedback and talked to the person about myself, and more importantly them.
It all amounts to knowing your buyer or seller. All that being said I would never send a cashier's check as payment in advance. Escrow services give help to both parties in expensive transactions.