hobbs switch is about $40
genuine sti waterspray nozzles are $22 ea
the dash switches are around $35 each i think
a neat trick is to utilise your disconnected in-guard airbox resonator for a water tank and just use a VT commodore washer pump

so probly around the $200-250 mark would be a good price installed

if you ar going to use something like the spec-c watertank that goes behind the rear seats add another few hundred