Yep, legitimate item. And very rare too. Be aware that there are two versions.
The first pattern uses leather for the pocket, elbow, shoulder and crotch flap reinforcements. The chest pockets are slanted, and the shoulder pocket has a flap cover. These are quite rare, and are no longer produced. I finally got my example this past year after looking for one for years.
The second pattern went back to Pattern 80 fabric for the reinforcements. The chest pockets are vertical, and the shoulder pocket is hidden, and closes with a zipper.
Price is a bit hard to nail down, as these things don't come up for sale often. The few examples I have to go by over the past couple years place Type 1 S2000 slangvels in the $250 to $350 range. Type 2 go for a bit less, around the $180 to $250 range.
It's also possible that you might encounter two other types, both of which are non-standard slangvels. This first one has been described as a prototype piece, and it very well might be, as I only know of one other like it. It is cut just like the type adopted by the SAP Special Task Force, with the sqare bottom pockets, and the zipper sides for wearing with a sidearm. As such, it was made by a legitimate contractor, even though it is devoid of any labels besides the size.
This second non-standard type has me be a bit puzzled. I've seen six or seven of these over the years, which is too many to be considered a prototype. They use a very dark green shade of Pattern 80 material, which I've never seen used in any other SADF/SANDF application. The pockets lack drain grommets, which are present on all issue slangvels. And again, there is a lack of a manufacturer tag, which is also present on all government issue slangvels. It's possible they could have been a limited trial batch, but every example I've seen is unissued, and trial items usually get the crap beat out of them. In any event, there are a couple of these floating around out there, so it's possible you might find one.
Hope this helps.
Cheers,
Mike