It's infuriating how if I buy, say, a dishwasher, and the heater pump goes, it's around £100 for a new one, but the whole machine costs maybe £400. Are you telling me that all that steel and plastic and motors and controllers and labor and profit and shipping and everything is actually 75% of the cost, and 25% of the entire value of my dishwasher is tied up in the value of that one part, the one that happened to need replacement?
And don't get me started on cars!
If we as species cared about sustainability (we don't), companies would have to sell their parts for little enough that you could buy all the parts for a whole new machine for no more than the cost of the new machine. That would focus their minds on using interchangeable, standard, COTS parts to avoid having to maintain SKUs and also avoid having the parts fail in the first place. Rather, now, it's highly profitable to make parts fail: you either get to ding the customer for a replacement part at 500% markup, or they give in and buy a whole new machine, and the old one goes to scrap.