Are you sure it wasn’t sold as a "B" grade item or something (’B’ for Brit 😁 ) while you were talking with him? got lost in translation somewhere? I ask because he did give you a "killer deal"... a killer deal for a handy man/self made/ hardworking carpenter apparently!....If that’s not the case and all the packaging seemed solid (didn’t look like it got bashed and fell 10 feet on a ship or something), it could be that he just screwed you.
For anything perceived as a "higher risk" purchase, you should consider making such a purchase with certain types of credit cards with very good "purchase protection" benefits. The good ones will cover up to 50k at times for a consumer card. Typically, they’ll require a very high credit score, an annual fee, etc (miniscule in comparison to the cost of hifi). In other words, all credit cards are not the same. You will need to go with the big banking dogs and not some wimpy li’l credit union... The big dogs have more ways to cover you and screw him.