I am thinking about my rotary table. It is a 12" rotary table with
full 4th axis control (G code, not M code). The only thing that it
lacks is a brake (and it is slow).

A comparable table costs $25,990.

http://vse.ats-s.com/SmartCatalogPor...D=Q6UJ9A00LTIA

The troyke table was $149 plus $150 for resolver converter. I also
bought an encoder card from Jon, but its cost allocation is shared
between the rotary table and the motor on the knee, so I would say
$100.

$100 + $149 + $150 = $399.

Add to this at least 50 hours of my time, which I am not sure how to
value.

i