It'd be a shame if he quit making the kits, but I can understand why. That'll always be a low volume specialty product, no matter how popular it gets. It'd be tough to break even, given the amount of research and development that must go into something like that. If you don't mind me asking, how many have been sold?
Maybe he could focus on reducing the costs of the kit by simplifying it or outsourcing production. If the price goes down, it can only help sales.
But I think it would be in his best interests to at least keep it offered for sale, even if it's on a "build to order" basis so he doesn't have to keep lots of inventory laying around.
I see these kits becoming more popular as the focuses get older. Before, it was hard to justify the costs of the swap when the cars and engines were new and relatively expensive. One of the first 03 cobra focus swaps I saw, some guy bought a brand new focus and a brand new 03 cobra. At the end of the day, he had a nice car, but then he had a brand new leftover 03 cobra chassis and a brand new focus engine. that's kind of a waste. $35,000 for the 03 cobra, and $20,000 for the focus. Now, you've got yourself a $55-60,000 focus with lots of leftover parts.
Nowadays, you can get everything you need from the junkyard. Find a focus with a blown engine for a couple grand, and then find a wrecked donor car for a couple grand. A couple grand for the kit and other parts, and you can have yourself a V8 focus for $10-$15 grand, if that!
With that being said, I only see the popularity of these kits improving. Especially if the company can help the customer find donor cars.