I paid about $350 for my frontbar to be painted and fitted from raw.. but i was getting some insurance work done at the same time so they may have charged me cheaper.
My 400R is 110mm off the ground, but I've got adjustable coilovers.. Depends on your setup? I definitely wouldn't go much lower than that, its already JUST bareable on most QLD can throw at it.. but it will die an eventual death.. I give it another 12-18 months till it needs replacement. If you go low and actually drive it, front bars are a throwout item.