It boils down to "price points." Though IM, JPS & Vintage all build Speedster replica's, they don't target the price point. JPS & Vintage are not competing with IM for the same potential buyers.
If budget isn't an issue, or refined features are desired, IM fills that nitch admiribly. You are paying a pretty penny, but on the other hand, it costs more to build a plush car.
I am not convinced that IM's steel tube frame adds much if anything to the sticker as compared to JPS & Vintage buying a wreck beetle, shortening its pan and refurbishing it. That process has a lot of labor. As the supply of beetles dries up I suspect Vw pans will get more expensive compared to jig-contructed steel tube frames.
You get a fine car from VIntage & JPS, for the sticker a real value. Their potentail buyer pool is different than IM's.
We are lucky there are three manufacturers who are all nice guys and all have good reputations with the vast majorities of their customers, regardless of price points.