The Palladio Company
Cambridge, MA
1-800-628-9618
10 sheets of 16x20 paper was $300 the last time I bought some (6
months ago?)
They also sell "Irregular" paper which has small defects that you can
usually work around with little or no problem for about 1/3 less $$.
I find their paper fairly flexible using hydrogen peroxide in the
developer for contrast control. Their paper tends to be inherenty
more contrasty than my hand-coated paper and works particularly well
with negatives that may have originally been intended for silver
printing (it also works well with "platinum" negatives, of course).
Kerik