Any question answered...

↑This, or less.
Take the cranks and PC-V(I*) and wiring harness off the price the complete kit made and you come to a negative number. There's a couple of PC-VI head units hovering around the $100 at the moment, but it's a big punt to go in for the head unit and spider separately.

You already have the cranks? Given that the one that went for £500 complete was too rich for your blood you should be reasonably confident that if you win the spider for under £100 then you can complete the kit for around £400.

He emailed me back about this, he'd accept a minimum of $900+postage for the power meter, wiring harness and (not working) PC-V, this after I emailed him the link to the complete, working, freshly batteried meter/harness/PC-V/cranks/Bottom bracket that went for $830.

NEXT!