You buy the scaler once, with these you buy each one of these for a fair bit of money for every console, and either put in the labor yourself or pay someone else to do the labor.
That is 100% my point! It's wasteful to buy what is essentially the same device over and over again when you only need one.
I'll admit the clarity of the CPS2 HDMI mod is nothing short of fantastic (even my precious OSSC setup has some visible noise in comparison).
But the awe is seriously downgraded when I need to spend 100$ or more plus installation efforts on each one of my devices.
Also at least in the case of the CPS2 HDMI device it only supports 1920x1080 in 5x mode (so the top and bottom of the screen is cropped).
OSSC supports 1600x1200 at 5x (so nothing is cropped)... If you don't own a 4k TV you likely don't care or have even noticed, but I both own and care about this feature.