I think there are many factors at play. The price of a new tractor is insane! Is that due to emissions or technology? There is a great debate. The other issue at play is a new tractor is loaded with so much technology and the tractor manufactures refuse to allow the owners the ability to diagnose the issues and fix them themselves that many of the farmers have strayed away. They have self driving features and so many redundant safety features that one small issue will prevent the small farmer from getting his crops put up before the rain comes in.
Your link to the 4440 JD. An equivalent new tractor of that size and capacity would likely cost $70-100K. The big advantage of something like the 4440 over a modern tractor is the farmer can fix the 4440 him/herself in the field without having to wait on JD for a service call.
Even the tractor models before the 4440 are demanding high prices and are still used in the fields for many smaller operations. The 4020 is one of the most reliable old tractors that are really simple to fix. These were produced from 1964-late 70’s. For a rebuilt 4020, I have seen prices range from $12K - $25K.
I have a 1964 3020 propane that I use around my place. I am not plowing fields or putting up crops. I use mine to pull a 10’ brush hog, feed cows/horses, doze brush, level driveway. I made many attachments to do a lot of the heavy work around the house. I have a forklift attachment that I made, boom pole, pile driver, hydraulic wire roller and unroller, tree pulling jaws, hydraulic clam bucket for dragging cut trees… Its an old tractor that will hopefully be in operation for the next 53 years. There is no computer and it is as basic and simple as possible. It has been modernized with a GM style alternator.