Lol, tell me you've never step inside a data center in your life without telling me.

Just because the US dominated market is wasteful and destructive doesn't mean it is like that everywhere. You buy a server today and the offerings will be the same CPUs that were available five years ago. Servers are mean, powerful beasts, and upgrades have been slow and incremental at best for almost two decades. While manufacturer guarantees might last 7 to 10 years, operators offer refurbishment and refreshment services with extended guarantees. A decade old server is not a rare sight in a data center, hell we even kept some old Windows servers from the XP area around. Also, mainframes are most definitely not legacy machinery. Modern and new mainframes are deployed even today. It is a particular mode and architecture quirk, but it is just another server at the end of the day. In fact, the z17 is an AI specialized mainframe that released just this year as a full stack ready made AI solution.

A business that replaces servers every 3 years is burning money and any sane CFO would kick the CTO in the nuts who made such a stupid decision without a very strong reason to do it. Though C suites are not known for being sane, it is mostly in the US that such kind of wastefulness is found. All this is from experience on the corporate IT side, not at all hobbyist or second hand market.