Most of the large multi-cylinder engines (more than 18 cylinders) went nowhere with only a few 24 cylinder engines being an exception. Reviews are mixed on the R-4360, it was always a bear for maintenance and may have been one of P&W least reliable engines. Not that major parts broke, but a host of minor issues. It should have been simple, take a bunch of R-2800 cylinders (heads, valves, rocker arms, pistons, rings etc) and instead of two rows of 9 use four rows of 7. And yet it took about 3 times the amount of money to develop the R-4360 as it did the R-2800. They had 3500 hours of run time in testing on the prototype and development engines of the "A" series R-2800 before the engine passed it's 150 hr type test. The R-4360 had 15,000 hours on 23 engines before it became "reliable", a condition that might be argued by many early crew chiefs and mechanics.
The cost of the Sabre in either man hours or money has never been revealed.