Not only a niche market, but how many of those guys are willing to pay $1500+ for a deal like that when they could swap in a V8 for similar money? Probably less than 10%. Now of that 10% niche of a niche market, how many of them have the cash? Needle in a haystack type deal if you ask me.
Plus, when you go to build one, you find out real quick that it costs just the same or sometimes more than a V8. That's a hard pill for customers to swallow. They figure less engine is less money. It's just not true.