I've just plugged these cities into Travelocity for the same date in September (just to get an idea) from Charleston to each, and here's what I came up with:
San Diego: About $400
San Francisco: About $420
Seattle: About $420.
Florida: I would just drive.
Charlotte: I would just drive.
NYC: About $250.
Boston: About $275.
So none are insane and from where I am to these cities, prices seem about right...
I still say SF or Boston
Plus, Nanci (YorkieChick1) is from there, and she has posted that a large group of yorkie owners locally might add to our numbers...just another thought...