I don't think "Price" is the answer to why VAC gear isn't more popular. In fact, it is rapidly gaining in popularity as more people hear about/hear it.
Kevin Hayes purposely doesn't advertise nor cater to reviewers as do many others, believing in putting out the best possible product at his various price points. He definitely puts his clients first. As he says on his website:
"The fact is, each VAC component is hand built as a labor of love, in a time intensive way, and has enough of a 'diehard' following that there is usually an 3-12 week backlog of orders, and thus no units available for review. We do not view this as a problem: there isn't anyway to meet the higher than current demand that a 'great review' might create. Our focus is on making the best gear possible, not the best-reviewed gear!"
The last sentence says it all, IMO. I appreciate this and know that it's true from my conversations with Kevin. He definitely "walks the talk". I will happily continue to own VAC gear and if asked will continue to recommend it. Just my $.02.