I just built 3, average cost each: $200. Yeah, they're minimal, but perfectly capable. I wired my office, den and living room for network cabling, so no WiFi cards needed.
- Compaq dc5800 mini-desktop with PCIx slot, $30-ish each (no HDD, 1GB ram, eBay)
- Ram to 4GB: about $21 each (1GB sticks $7 on eBay)
- HDD: $29 each for 500GB SATA (newEgg -- cheapest SATA drive they had listed at the time, not refurb)
- GeForce GT 640: $60 average ($80, $70, $70-40 rebate, newEgg)
- Windows 7 COA: $29 each (eBay)
- drive screws because the dc5800s have those weird "modular, slide-in" drive bays: $4 per machine ($1 per screw, eBay)
- various keyboard, trackball, mouse either from my parts box or whatever (free or insignificantly cheap)
Your mileage may very, of course, but you can create a new low-range machine for about $200. And by low-range I mean more than enough to play CoH on pretty high settings.
The graphics cards came with low-profile slot adapters, and they have HDMI as well as DVI and VGA, so you can use your TVs as monitors. I happen to have two 22" (one personal, one for work, but I work from home), and an old 32" TV that does 1080p, so I didn't need monitors either. That would cost you maybe an extra $100 per machine if you had to add it.