While you have good points and that is certainly the counter argument... You are always, always paying for hardware regardless unless you're willing to run on old systems, so that point is effectively moot. And many companies don't really have time to deal with the after market. They'd make more money dealing within their core business than spending time trying to sell their stuff on KSL or whatever while also refreshing the PC so their data is no longer on it. Some of the most poorly run companies are the ones that have highly paid people dealing with trivial tasks outside of what they're being paid to do.
My point is the strict cost of hardware isn't the only factor.
For many businesses who've researched this out and considered both strategies they've opted for what I proposed and they make more money doing it this way.
So..... Not a horrible idea....for some....