I just signed a renewal for $15.33/sq ft., which I find to be “reasonable” in my market. So, $15.50 may not be out of line depending upon the locale. However, remember that “everything is negotiable.” If you’re really dead set on opening a store at this location, make a counter offer that is several dollars less per square foot in the 1st year or two and slowly builds up to what the landlord is asking much later in the lease.
Also: I know most of the posters on here love long-term leases, but ask yourself what happens if you enter into a 5-year lease and your business dies an untimely death after a year or two. I just closed a location in June that we signed up for 5 years instead of another place with much lower rent plus percentage rent on a 3-year deal. I would have never paid a dime in percentage rent, saved myself a pile in build out, and been out of there 2 years sooner if I had “accounted for failure and dealt with success” instead of the other way around.
I hope you are successful, but please think about “what happens if this doesn’t work?”