I've seen a few cars on Ebay with good descriptions and photos never make reserve, and I would guess, that's by design. Let's say you've just completed a high end restoration and want to see what the market thinks it's worth. You add up your purchase price of the original car and all receipts and that's your reserve. Fortunately/unfortunately, depending upon your perspective, our cars rarely bring what it cost to restore them...even when discounting the labor.
It's been stated that top concours price for a '65 Midget is $16,000. That's according to someone's guide. Based upon what...recent Ebay auctions? Private sales? NADA? I've never seen a '65 (or any other year) Midget offered on Ebay with a DOCUMENTED concours history. Why? Because the top cars of that category usually trade pivately. Any car that has ever placed in the topmost tier of a nationally or internationally recognized concours has brought with it at least several offers of the nature "If you ever decide to sell that car, call me".
I can tell you this, you'll not build a top concours car for $16,000...you'd be hard pressed to do so for double that amount.
Now, suppose a Big Healey cost $XXXXX new and a similar vintage Midget or Sprite half of that. That, to me, is probably the least important consideration with regard to today's value. Parts cost...yes, there's gonna be some difference...that can be documented by anyone with a catalog. Donor cars...yes, some difference in cost there. Labor, not a lot of difference. The biggest difference though will always be in either rarity and/or desirability, perceived or otherwise. Can't just go by production figures either...I read the other day that something like 80% of all Ferraris ever produced still exist. Our cars, unlike Ferraris (or Big Healeys), were throw aways...so, how many were kept pristene?
Ray