Absolutely a scam. The biggest clue is that private shipping company. If you followed through, you'd lose both your item and the "overage" from the cashier's check (they'd send you extra and ask you to refund the overage - since the cashier's check is no good, you'd lose that money).
They usually target high-end items and often look for newbies.
Other clues:
Poor English
Asking you to respond outside the Etsy system
Asking questions about an item that are clearly answered in the item description
