My only experience with Kinko's was $50 each for 16 x 16 mounted on gatorboard with clear laminate surface.
As for output from SU - render a jpg (best quality setting in the options dialog) as big as you can (max. is 9999 pixels) WITHOUT ANTIALIASING, then import into Pshop and resize down with bicubic resampling. Pshop will do the antialising much better than SU and almost instantaneously (and SU will tend to freeze with AA output above 3000 pixels, not to mention taking forever).