Well, this isn't really talking about HTPCs in the sense of playing back HD movies. Granted, if the movie is in Windows Media format you could play it on a 360 through MCE; but what about other formats? With an HTPC and a Blu Ray drive you could watch Blu Rays, and for $130 (BD ROM) and a spare semi-modern PC, that's what you'll get.
Companies like this, which in all probability paid TH, make massive profit margins off of their products. As well built as it may be and as easy as it could be to use, the actual hardware can be obtained for much cheaper and the software could all be replaced with something like MythTV, which happens to be free. The one thing I will say about their 12TB solution is that it requires 13 hard drives and an expensive PCIe RAID5 controller. The controller is probably $500, and each drive is around $180. Retail cost of around $2700 just for the array subsystem. Then you need to find a case to house the drives (pretty common 13 drive rackmount units), which is usually a couple hundred more. The use of dual Xeons, for all we know are using 2 of the $1000 CPU variety. Of course the board is going to be expensive. And the power supply needs to be pretty good. Not to mention the 8 CableCARD devices, which obviously need some sort of special interconnect since boards don't have 8 PCIe slots (10 with the graphics and RAID). All in all, we're probably looking at around $6500-$7000 in hardware costs. The rest is simply installation, configuration, warranty, and of course, profit.
My HTPC is only used for playback, but for $150 and being a couple years old, I have to admit it's able to playback 1080p with DTS without any problems (X2 4200+, 2GB RAM). If I wanted it to record HD, the hard drive (Seagate 7200.7 120GB) would never work and to be able to encode from M2TS files into x264 would take longer than its worth.