Well I'm not going to argue with Keith because he probably knows every nut, bolt and lock washer better than just about any one, but I will say this. There are probably 2-3 kinds of people that will buy a performance car:
A) The fat, happy, lazy, etc. person who gets their miata/boxter/etc with all the fixins and seriously considers getting it with an automatic - or actually does so. Chances are this is going to be a weekend/sunny day car anyway. Advertise to these people as you are right, they are probably 80-90% of the market.
B) Folks are buying these as daily drivers and are somewhat of an enthusiast or someone who can't afford/has enough space/etc to keep two cars and wants a double-duty car that gets them too and from work during the 9-5 and they can track/autox on the weekends if they wish. Chances are these folks will eventually filter into the former or latter category.
C) The true/borderline committed enthusiast who is going to drive it only on the weekends, probably to and from whatever event they are participating in, and maybe on the occassional club run to the local tech session, clam shack or coffee house. Chances are they are going to buy a second hand car unless they can afford to buy new, and if they get hooked, are going to start yoinking stuff out to be competitive.
All I'm saying is that there should be some base starting point like there used to be in the good old days. A base model that doesn't have the bells and whistles, body kits and tupperware, that someone who is looking to get into a performance car at the lowest price point possible can still do. The fact that not having all the baubles and bolt-ons save 250 pounds is a bonus.
I see no reason in this day and age why you shouldn't be able to get into a base model, stripped down miata for right around $20K. A Boxster for around $40-45K.
And if the model doesn't work, why is the Elise such a popular car?
I'd bet that if there was a lightweight, stripped down, decent looking car that cost around $20k (or less) and had performance half as good as the Elise (0-60 in ~6 seconds, skidpad numbers in the .90+G area, 50-50 weight dist., 2300 lbs or better, ~150 hp or better, etc.), they'd get sold right quick. These don't seem like impossible numbers to me.