Indeed. Using a CPU as a heater is just silly, it would be like frying an egg on the engine block of your Ferrari: technically possible but there are better and cheaper ways to get the same thing done. It wouldn't be that hard to hack together a decent computer controlled heater and sample holder/heat exchanger from a few hundred to a thousand bucks in parts (depending on how much labor you want to put into it).
Instead they have this fiddly system where they have to load samples onto the heatsink of a running computer with the motherboard out in the open, and they must be careful not to drop anything onto the motherboard which could damage it, there are ESD damage concerns, and liquid damage concerns. The temperature control cannot be that good, given the vertical temperature gradient along the heatsink base to top.
It's also disingenuous (but common) for them to merely compare the raw part cost of a DIY system to a pro system. The Pro system is much more capable and robust, support is available, and it includes the labor cost of designing and assembling it. Too many DIY projects claim a "cost" which treats labor as a free commodity.