Alibaba, for the most part, is wholesale. That item in particular is a minimum order of 300 pieces.
$10-$20 will be the scaled price per unit. If you buy the minimum order (300 pieces) you'll pay $20 each ($6,000). If you bought a huge order (probably 1,000+ pieces) you'd get the lower price at $10 each ($10,000).
If you like that specific case, browse Aliexpress - it's part of Alibaba, but more of a retail to small wholesale (like 50 pieces or so) space.
It's not likely to be of high quality construction, and I wouldn't bank on the front connectors or USB working for long (if at all) due to cost cutting measures to keep the price down, but not likely to be any worse than the cheapest cases you can buy locally.
pepslight :
Still a dead link.
One thing I learned is never buy nonstandard cases, meaning you will have problem fitting components inside,
The link just appears to be an issue for you. The original link worked fine for me (and, as it appears, rgd too), and the second.
I wouldn't have too much of a concern with non-standard dimensions etc, provided it reviews fairly well. If it doesn't fit an ATX/mATX/ITX board as you expect, that would show up in review #1 or #2, if legit reviews.