Your point is well made and yes we all want our trucks to not require a major repair outside of warranty and especially right after the warranty has expired, but all the manufactures have to draw the line when it comes to a repair outside the warranty period and your truck crossed that line.
I've been in your shoes when I had to fund 3 injectors on a RAM cummins that was out of warranty both by ~2 years and ~15k miles. When I purchased the used truck 3 injectors were already replaced by the original owner, and two went bad after I purchased the truck so while it was already being torn into for the two bad injectors I went ahead and payed to replace the 3rd and last good injector hoping this would be the end of this non sense. I hope you also replaced the eighth good injector because it's probably on it's way out too.
My 6.0 PSD at 170k miles had all original injectors with no signs of problems when I traded it in, but I only used OEM fuel filters which I'm curious what brand of fuel filters did you use?