The price is the first thing that shuts most people down with video pins. Assuming you use quality components (decent screens and powerful enough PC) you're not going to come in much under $3.5k just in parts. Add in labour time, support, liability insurance, etc and yep, retail cab ends up $5k to make it worthwhile.
Took us 6 months of prototyping and 7 builds to work that out ;)
Sure you can cut corners of the PC, score a cheap old junker cab or use Kogan screens but a video-pin is an expensive toy no matter how you cut it.
The people ask me about a real DMD or force back, which just adds even more to the build cost!
Now that the Infinity base cab is "out" I'm looking for an affordable forcefeed back solution. The big trick for us is to keep it at 12v if possible. Been looking at the U-HID boards too.