knock 10 bux off the asking price for every 100mhz over 3.9ghz the cpu was overclocked.
so if it was oc'd to 4.4ghx knock 50 off the asking price as it was oc'd 500mhz or .5ghz over the boost clock speed.
its my personal rule of thumb and is a good starting point to haggle from. dont be scared to low ball him either. the higher the oc the less value is in the chip.
and dont take his word that he never oc'd it. if it was in a k series motherboard then theres more than a good chance its been oc'd at some point.
http://www.ebay.co.uk/itm/Intel-Core-i7-3770K-3770K-3-5GHz-Quad-Core-CM8063701211700-Processor-/122008802313 £125 buy now price works out at $180 so no mate 185 isnt a great bargain.
thats also the first chip i came across theres likely to be cheaper to be had.