The kit car market is unique, especially at the higher end.
Somebody, like us, who's into it will try to get a car for pennies on the dollar. We'll argue why the car doesn't deserve a top premium price tag, because of the parts used, or because it was self-assembled.
So the trick is not to sell to this market. You're looking for somebody who loves the idea/concept of what you have and is willing to pay for it.
I've seen a donor 5.0 ffr cobra go for 90k up here. One of my old work colleagues was willing to trade his gallardo straight up for my cobra after 1 drive in it (it only took a five minute spirited jaunt in it for him to see it was superior to his lambo in everyway, save creature comforts and safety).
If you have (for e.g.,) a cobra and try to sell it on ebay, ffrcobra.com, or cobracountry (or whatever it's called), expect to get kicked in the balls - the people who stop there know then can knock it down by using the typical kit car arguments, so you have to avoid them. Tedious - yes. Longer sale time - yes. But higher prices in the end.
This isn't a comment about "the market" but more about my own thinking: when I first started looking I thought Roush was the way to go. But I almost immediately noticed a far out-of-proportion number of problem reports from Roush owners. Then when I compared prices while carefully accounting for what came with the engines from different vendors (eg ign. box, bell housing, clutch, etc.) I concluded that the several thousand-dollar Roush tax was for vapor and that I wasn't going to pay it. Will I be sorry at resale time? Maybe. Or maybe that day never comes.
Same here - I was initially going to buy a rousch 427r for my cobra, but saw the sheer number of problems people were having with their engines. Plus the warranty was hit or miss, so it was like 'why bother'.
Resale ... who knows. It might have an impact because a lot of people are stupid are want the namesake of something rather than the quality/performance, but I don't think any/many of us build with the idea of resale in mind.