"Ok so I got offered 3.4k Tops time and time again against 04/03 350z's with 60k on the clock." Seems a tiny bit low to me but not by much, remember the OP's is a year or two newer than that which does make quite a difference to the value. When I was looking to buy it was generally around £11-13K for an MY07 onwards, £9-11K for an MY06 and then down to £4K for an MY03. So if you traded an 03 in for £3.4K the dealer would probaly only be able to sell it for around £4k to £5K at a push and so when you think about it that's only a profit of between £600-£1600 bearing in mind they will probably have to pay for a service and MOT and anything else that is wrong with it (tyres, brakes, exhaust, suspension parts - all of which cost quite abit on the Z even for a dealer)