It's kinda tough to explain, but my rationale is that I plan on mine becoming a daily driver. While '71-'73s are becoming more 'rare' (as Mustangs go, with the added 'lesser value' because they stray a bit from the more accepted 'classic Mustang' look), my H-code isn't a particularly valuable (or highly sought-after) model... such as a Q, R, or even M code. Everybody goes searching for '71-'73s hoping to find that elusive Boss 351 in someone's garage for cheap because the owner's widow just wants it gone... but usually wind up 'settling' for an H-code because that's all they can find within the range of money they wanted to spend. Me - not so much... I simply wanted a '71 Mach 1, regardless of the engine because I'm all about restomod, and had no intentions of preserving history (just saving an example of my favorite Mustang for myself).
Therefore, get it back together and enjoy it as a daily driver is my plan. If it gets a little dinged up, rock chips, or even blows the engine, I'll be fine repairing it and moving on.
If I were to plunk down $50K+ on a fine specimen 'rare' model, I'd have a much harder time subjecting it to the rigors of being a daily driver. I would just feel guilty (weird, whatever) about buying a 90-point show car, slapping on some Cragars, and parking it at the local grocery store on the way home from work - over and over and over again throughout the course of its [and what's left of my] life.
Something like the one offered up in the original post? Weekend cruise nights, parades, car shows, etc. (my opinion) - not daily driver.
I guess I haven't grown up yet or been successful enough or something. I just can't imagine me ever driving a $40-50K car for just 'transportation' purposes.