What is the price of calligraphy in Ding Foyan?

Ding Foyan's paintings and calligraphy works were recently auctioned in Di Chin, Henan (May 3, 2008) and Hanhai, Beijing (April 4, 2008-19), with an average transaction price of 2000-2500 yuan/square foot. The attached drawing is an enlarged view signed and sealed by one of them: