Dean Jones says:

"Why should I offer you more than the 55th percentile?"

Your response:

1.  I'll answer your question if you'll answer mine:  What are you looking for in an Assistant Professor that would justify paying a higher salary?

2.  You will be hiring an excellent, dynamic teacher, as well as a thought leader in my field of research.  Have you seen my "Google Scholar" numbers (reflecting the number of times other researchers have cited my work)?  For a fresh Ph.D., they are "off the charts!"

3.  I have another offer 'in-hand' that is at the 71st percentile.  However, I like your university better.  If you can match their offer, I'd prefer working here.