https://timbergroveenterprises.com/old-home
About $350 but quality materials no cheap plastic lines & brass fittings instead of plastic and heavy rubber bags that as seen in picture is between axle & frame not inside the spring. Leaks are much less likely. Also requires less psi to carry the same load when compared to in coil bags. So it dampens and controls the rear suspension under heavy load and rough pot holes etc much better.
But I get it the cheap $100 in coils bags sufficed in previous vehicles. But now 590,000 miles towing TT/THs & boats commercially sometimes with a Harley etc in the bed has me spoiled to axle to frame set ups.
BTW this is a no cut no drill do it yourself install see installation video. Also you don’t need an expensive on board compressor set up. Any cheap portable cigarette lighter or dash plug in as the 4th gens have Harbor Freight, Walmart etc unit that stores under your seat quickly inflates them as you only ever need like 20 psi.