Let's say you have a hankering to experience a V8 Miata. Not for very long, but long enough that you would need to own said Miata.
Let's also say that you currently lack the time, space, and energy to wrench on a modified car for weekends at a time.
Let's finally say that you've saved enough cash to spend anywhere between "$10k and good luck, taillight warranty" and "$50k Flyin Miata package, drop off, write check, pick up."
How about somewhere in the middle?
I assume having a shop build your car is always going to be a money-losing proposition. Fair enough. What about a used example, built by a reputable shop, like the one on FM's website right now?
https://www.flyinmiata.com/V8/for_sale.html
In theory, knowing nothing about the used Flyin Miata-built V8 market (yet), that car should hold most of that value, or at least enough that you wouldn't lose more money than you would either building your own, or fixing someone else's project. Which is true of any build-vs-buy scenario, except in this one, the "buy" doesn't involve a hacked up wiring harness and stripped out oil pan (hopefully).
There are outliers in every hypothetical. Can you find a privately built Miata to rival Flyin' Miata quality? Sure. Will it carry the same rapport when it comes to sell? Almost certainly not. "Built By Flyin Miata" sounds a lot better than "The Guy I Bought It From Seemed To Know What He's Doing."
Am I on the right track here? This is disregarding the opportunity cost for the cash, let's say it's negligible due to the short timeframe (1-2 years). It's also disregarding any personal enjoyment from building your own, sense of ownership, etc.