you'ld be immensely lucky to get an 05 636 in pristine condition for that price. $6000 is the fair rate with just a "sprinkle" of luck, 6,300 is the average.5K ish.... if it's in premo condition.
does it have sliders installed?
how do the tires look, have they been replaced yet?
any aftermarket stuff, or is it stock?
how's the brake fluid look?
how does the chain look, dirty or clean? has it been lubed regulaly?
is there a service history with the bike?
somewhere on here there is a very extensive thread on buying a used bike. Good luck , those are great bikes!!!!!!!!:mfclap