Cessna 172s are great if you are learning to fly. But most people using these things for actually getting from A to B will be looking for something with a bit more range, speed, etc. That still might be sixty year old plane but one with a bigger engine; or two of them even. And if you want to go really fast you get something with a turbo prop or even jet engines. The newer ones are a bit more efficient with the fuel but also more in demand and therefore more expensive. You get what you pay for.
My understanding of the aviation market is that there are some bargains to be had with planes that are old but still very servicable. But if you are flying longer distances regularly, you kind of gravitate towards the more expensive ones. Because they go faster, use less fuel, are more comfortable, have more useful load, etc.
The point of a tractor is that is used to do useful work by farmers who earn their living working these things hard. If they break down, work stops until that can be fixed. The value of being able to fix these machines yourself is that you get them back in action quickly. But the value of a newer one is that it presumably wouldn't need a lot of fixing to begin with. And maximizing power while minimizing fuel usage means the job gets done quicker and at a lower cost. And that's what modern manufacturers sell of course.
IMHO, electric is going to revolutionize farming. Diesel is expensive (a lot more lately). And farmers burn a lot of it. Electric motors are small, reliable, quiet, etc. They have loads of torque. And if you are a farmer, you have plenty of space to harvest your own electricity with solar panels and maybe a wind mill and some batteries. There is a growing amount of high end stuff available in this space but also very affordable low end stuff. And this technology can be very simple and tinker friendly. Buy some old EV batteries wire them up and you can make anything with wheels move. Including really old tractors, pickup trucks, etc. Anything from the largest mining trucks to the smallest lawn mower can already be powered by batteries. And everything in between. With battery cost dropping, there are very few obstacles that prevent adoption left. Mostly import tariffs in the US.