I came across this website http://www.motion-sim.com/
They have developed a 3 and 4 DoF platform which looks similar to the ForceDynamic system. Performance looks quite good. Payload 300kg.

Some videos (mostly car racing) http://www.youtube.com/user/milapatek#p/u/0/c3CaoeV9g0E

The system seems to be build using asynchronous motors driving cogged belt. Powered from 230V single phase.

I'm still curious how they solve the weight balance issue.

The website also gives pricing for the different systems. Still a lot of cash, but prices seem to be lower than the indications Forcedynamics used to give.