Like others have said, the price is way over what current market value, which I'd place at around $800. Among vintage US-made vintage drums, Slingerland are the least valued (some would say undervalued, but that's a whole other discussion), and since the seller doesn't bother taking a shot of the ride, crash, and hi-hat cymbals and their stamps (more about that below), it's difficult to determine whether the cymbals add any value or are just more crap that whomever buys these will have to dispose of somehow..
The photos are absolutely terrible, and I'm not talking about focus or lighting, but rather composition, as the drums in the "master shot" are not set up properly and are posed in front of what appears to be a storage locker. Situated as they are among poorly placed accessories, the whole thing looks like a load of clutter that someone just bought for cheap at a storage locker auction, and the seller is another one of those Storage Wars a$$hats looking to "strike it rich". The video is equally as useless.
The "detail" shots show one right thing (the Slingerland badge) but the rest are all the wrong things like sticks, cymbal bags, drum cases (which looks like there are more cases than drums) - things utterly irrelevant to someone interested in a 50-year drum kit.
The response given to the question about drum size - "..Mounted Tom - 13" x 10" Snare - 15" x 6 1/4" Floor Tom - 17" x 17" Bass - 20 3/4" x 16"..", reveal the seller to be utterly clueless as to what he is selling, which casts doubt on the whole enterprise since one cannot believe what they are being told about a particular thing if the person doing the telling has no idea as to what they are talking about.
And that, my friends, is why these haven't sold.