I have installed Supco SPP6 and SPP6e on two RV rooftop ACs with good results. The SPP6e costs more but is a improved design that has a backup electronic timer to further protect the compressor vs. the basic SPP6. The cost of the units is under $ 15 and $ 25. These don't replace the Start/Run Capacitor, they install in parallel with the Run Capacitor.
If your AC is 7 years old or older, then you may also want to spend another $ 20 and replace the OEM Start/Run Capacitor at the same time, as they do slowly degrade over time.
I can't see where there would be enough incremental functionality to justify the ten times more expensive unit.
Randy - Manhattan, Kansas
2015 Vista 27N
2016 Honda HR-V