I can remember in the 70s going to Sears and looking at riding mowers. They had two classes back then. Both 8 HP and 12 HP models. The 8 HP was the basic model while the 12 HP was the deluxe. My last rider I bought from Sears was sometime in the mid 80s. It had an American made Briggs 12.5 HP in it. While it was a good mower it wasn't the great mower that some here seam to think they built back then. It wasn't expensive so my expectations were never that high. After about 10 years of average mowing on flat ground never towing anything the engine started having a problem where it would run fine but once it bogged down in taller grass it would suck up oil and smoke like crazy. Most likely a broken ring. A few years after that the mower deck rusted out because it was made out of thin metal. The spindles for the blades would break if the blade hit something unseen. The 5 speed manual gear box has bushings in it and they wore out so as it heated up from normal use the clay based grease would leak out. I'm positive that I said the same thing as you're saying now, that they didn't build them like they use to.
The real fact was that I didn't want to spend more money than I did. My last riding mower was a cheap Troy Built from Lowes. It has a belt based variable speed transmission that has worked very well. But the forward and reverse is done with the same transmission as in that old Sears rider I was talking about. Like the old Sears it wore out in the same way and the reverse gear started not fully engaging. The engine, and American made Kohler was the biggest POS I have ever seen. I have a Chinese made Harbor Freight engine that is a much better engine. Mine seams to be a better example than others. Below is a video someone else took of theirs running with a split block.
I can say for a fact that my X500 is in a different class. The deck is a lot thicker steel. It has grease fittings all over it. A simple search shows 12 year old versions with 1000 hours on them still selling for $2000 that run great. Simply keeping up on the maintenance shows that it will last a very long time. My yard is steep and rough. After two years the Troy Built was starting to self destruct. The brakes stopped working. The X500 is no different today, 4 years later, as the first time I mowed with it. I'm sure that it will last 20 years of mowing with me putting about 60 hours a year on it. The $2000 Troy Built might of been good for 5 years on my property however with the brakes (which were part of the transmission) and reverse not working right it most likely was going to cost hundreds to fix every few years. Had I stayed at my old house with the flat mostly smooth ground it would be doing much better now. I'm in the unique position were I can really put a rider to the test. However until moving here I would never have spent $5k on a riding mower.