I am curious if you have even driven an S30 of any variation and a current model Mustang?
I have owned a 2+2 up until recently, and been in a few 2-seaters (240z & 260z). Now i have never owned a mustang, but have covered a decent chunk of the US in a 2019 model, and would happily do so in one again, heck i'd even own one as a daily. Its good for long drives, comfy & all the mod-cons, but i tell you what, driving a S30 on the weekends, as most would not have an S30 for a daily now, it puts a smile on my face every time. There is something you get from driving an old Japanese classic, heck even a 90s JDM car, that you will never get from driving a heavy, modern & "safe" car such as a Mustang or even 370z. I am guessing you probably can't afford a new-ish Mustang, so maybe you should buy a Toyota 86 first.
also, as someone who really wants a 2-seater, I am also upset at the current prices, and have probably missed that boat, unless I sell my new born (jurys not out on that one yet), I can also appreciate to current prices on decent 2-seaters in Australia. HLS30s in the US in similar standard probably fetch for just as much, if not more over there. Even in Japan, S30s are getting up there.
So you are saying, all of these sellers are wankers? I doubt they are.......well maybe this guy https://www.gumtree.com.au/s-ad/west-ryde/cars-vans-utes/1976-datsun-240z-red/1239391979 but you can't put everyone in the same boat. Maybe it's the people who are buying the said "overpriced" S30s that are the wankers?
Maybe try go buy a fastback Mustang, and then go let the current owners know how you feel as well.
P.S. anyone selling a running rust free S30 2-seater for under $30k?