The hardtail version of the Sbike 808 came with them as standard in either 1992 or 1993 (still figuring out the exact year of production). Same with the 909. No idea about other brands, as I'm not an expert on those.
Exact specs are hard to find, but I think that back in the days you only had the HS11 and HS11 RaceLine.
So yes, they've been around for close to 20 years, and haven't been developed that much over time. A tweak here, a new component there, and that's it really.
However the 808, the cheapest SBike they came with, was around £2600 ... in the early 90s. That was during the big economic recession. I guess that gives a good indication of what I mean with "high-end".
The brand of the bike is also important if you want to put Maguras on a bike and stay period-correct.
In Europe they had a rather big following and as a result the European manufacturers put them on their bikes, which is why they stayed in production until today. The Americans however mostly ignored them in favor of early disc brakes.
So if you're building an American-made bike and want to remain period-correct, stay clear of Maguras or any other type of hydraulic rim brake.