We can all argue in circles till blue in the face on this.
From one perspective you could say shifter kart #/endthread
I have been looking an thinking for quite awhile. Once I have a job in my field and I can save for a bit and settle down here is the answer I have arrived at.
F500 car
For previous example of laptimes at Summit Point, the class record is 1'17.1"
You can buy a used road race ready car for $6k often with spares (few sets of wheels, engine(s), etc)
Forget about paying for shocks, you just replace the rubber pucks every year or so. Yes, you have to learn to tune a 2-smoke and a CVT, also they make perhaps the most annoying sound in the world. BUT, they are cheap.
Adding to the cheapness, they weigh 800lbs WITH DRIVER. that allows you to pull it on a RATHER small trailer. So cancel the big truck requirement of trailering other cars.
CSR/DSR, I find very interesting. F500 is just a cheaper option. (no shocks, no wings, no LSD/halfshafts etc, so fewer parts and cheaper)
You also have the interesting future of F600.
The F600 is the same car, ~800lbs with driver, no springs/shocks, no wings, and a 600cc sport bike motor in place of the snowmobile 2smoke and cvt.
added bonus on an f500 car, less then a days work to change from competitive RR spec to competitive FM AX spec.
That said, you could likely beat it with a laydown endurokart, but thats a safety tradeoff that crosses my line.