Had a few wr450,s over the years, its an 06 model looking at the exhaust, could be an 05 with 06 exhaust though. if its an 06 the speedo will be digital, get the vin number and ring yam uk who will tell you whilst you,re on the phone the year of manufacture and when it was first reg.
there is no way the bike is worth what hes asking even if its an 06, i just bought a 2008 alloy frame wr450 model with 1200 miles on the clock for �2950.
you,d be much better to sell your bike as a private sale and buy a wr with cash on the hip.