Hey there, nice bike you have here. How long have you had it?
A few weeks.  Rode it for 40miles only.  I'm just too big for it :/
Ahhh, thank goodness I'm tall and lanky then. My budget is limited but I promise I'll take good care of the bike.
I put a lot of work into it. So I'm glad to hear. What amount you have in mind?
Closer to 1000. My budget is 750 so I'm trying to make you a reasonable offer.
Oh no way man.  Only 40miles.  If I don't get 1500 I lose on this deal. 
Well that's fine, that's just unreasonable; I can't offer list price, sorry.
1500 is below list. Just saying.