I don't see why comparing prices between used and new options is unreasonable in this case. If I want a machine to do XYZ (without the stipulation that it be new), then an older model might well be better value. "In $CURRENT_YEAR, how can I get X processing power?"
Of course, old Macs should factor into that too. Also, it's a different story if I do want something brand new.
Here it’s because the old PC they picked is worse in every way than the brand new PC, except for RAM, which the Mac largely mitigates by having ludicrously fast flash hanging off the CPU. Of course an older, worse PC is going to be cheaper than a new Mac. (Except in this case, buying the boat anchor saves you a whopping $20. It’s not even better specs for the same price: it’s worse than the Apple gear that costs the same.)
If we want to compare new vs used, then how much would you have to spend to buy a brand new PC laptop as powerful as last year’s MacBook Pro?
Of course, old Macs should factor into that too. Also, it's a different story if I do want something brand new.