Sorry, mate ... I misread the original post. The fella I know already has the Akra headers but the end can is not from the same system and it's knackering the mid-range performance. He just needs the pukka Akra can (60mm outlet, IIRC) and those can be found on ebay so best you sell the complete system as one.
A thing is worth what someone's prepared to pay for it but those Akra systems used to be around £850 - £900 new before they were discontinued. Why not check ebay for a while to get a feel for prices - a few R1 systems of that vintage still appear and they seem to go for £350 - £400.
