The $650 build is called out as a gamer, and I don't think it is too unreasonable to assume that "enthusiasts" are also gamers, but I definitely think the "Professional" build must be targeted to a specific [type of] user, who perhaps only wishes to play games as an afterthought.
The problem is that the way these are scored only counts performance, and counts it linearly. While it would be very hard to objectively score on qualities like appearance, I think it would be possible to create a non-linear scale for performance, such that FPS up to 60 scores at one rate, FPS up to 90 scores at a second, lower rate, and FPS over that scores at the lowest incremental rate; more granularity can be introduced, and someone specifically going for 3D gaming would also score differently, but conceptually this could be done to illustrate that faster may be better, but only up to a point, after which it may become less irrelevant.
To apply this in a real world example, I play on one monitor, and I can use max settings in my mostly older and/or less demanding titles on a HD7870 and get smooth frame rates. A HD7970, though providing measurably faster FPS, doesn't "play" any smoother, so it is of no greater value to me. Someone playing Crysis 3 or Tomb Raider is obviously going to feel differently, but at some point the concept of diminishing returns will apply. Once I've met my primary performance targets, secondary measures like power use and noise become a lot more important, as do more subjective measures like size, appearance, and convenience. If the Professional is an accountant, perhaps his idea of a sweet build incorporates RAID1 and a UPS for data safety, and looks distinctly professional sitting beside his desk, or maybe it lives in a pair of 2U chassis in a rack against the wall.