While I appreciate the analysis and write-up of your maintenance and costs of the two classes, I would just like to note that I’ve had almost none of the issues you’ve described with your Yamaha in around 6-7 years of racing the class. Running dry clutches I’ve had almost no failures, even when I ran Yamaha Pipe on a 3-disk dry clutch (something most people generally thought was a tad unreasonable when slipping to 10k). I’ve used like 3 starters in my 13 years of racing.
It sounds like you had some bad luck with your Yamaha stuff.
I’ll also note that in my more limited Rotax experience I have had almost no reliability issues either. But the engine is a PITA to adjust the carb on and it’s absolutely zero fun to drive.