SIG is the new "HK." They have been able to position themselves on the market well. Their product line has depth, and the models come in a lengthy variety of sub models.
There is also the New! factor, and SIG does have the provenance of being military issue in more than one first tier government, including ours. Those departments and shooters who aren't saddled with the Beretta M9 can elect to carry SIG's and they do every time.
If you want to have something "better" than another boring run of the mill AR, you look elsewhere in the current marketplace, and SIG delivers to that buyer with US production based pricing. Poor HK has to get a permit from the German government to do anything these days and still suffers from the exchange rate. SIG didn't miss the boat by having the American plant independent of the Euro market. They are at the beginning of what appears to be their heyday. HK is however in serious decline and it's not going well. That has a lot to do with it from the perspective of their shared demographic buyer.
We aren't talking commodity guns in this market segment.