I didn't see that ... but I did read a DAILY inventory of 400,000,000 to 600,000,000 stamps filling 12,000 to 15,000 orders daily ... with sales of $468,000,000 in 2009! Actually that divides out to $1.282 million PER DAY in sales!
Just think what the sales must be in 2011 with all the new issues and the increased postage rates that just came out a month or two ago.
Actually, for those interested more in "The Cave" than the USPS, I would point you to the SubTropolis website where they have rather interesting videos showing this massive complex, the USPS being only one of many major tenants:
http://www.huntmidwest.com/subtropolis/movies.html