What Does "Reasonable Offer" mean?

I picked up a small block six pack manifold topped with 440 carbs for $800 last week. Selling price was $1000, I offered $700 which was rejected, then after about 5 minutes of Hm'n and Ha'n I increased my offer to $800 and we both shook hands and walked away happy.

So, a reasonable offer might simply be the one where both people walk way happy.