noted steve
*assuming you could buy a 6month old supercharger that was removed from a damaged mk2
*say it needed a new cross over tube which you bought from moss usa for $80
*supposing it came with BRP idler tensioners( similar to the TDR)
say you bought the kit for £1000 sterling
i would imagine a person with good knowledge of the mx5 could possibly charge £135 for fitting of the basic mechanicals, ie charger and belt etc
supposing that you didnt want the begi afpr that came with the basic kit and wanted a AEM FIC fitted
a good used AEM FIC should cost around £300 ( still under warranty from eastcoast customs in co.down)
the time consuming part would be the wiring install
but supposing you were to arrive with a mk1 1,8 patch lead ( available from AEM) or a pre wired harness from boom slang , then i would imagine the person fitting wouldnt charge you anything at all.

all you would need is to get it tuned for your car on a rolling road , which you would have the usb cable and software on your laptop
all supposing , of course