I just got a brand new Undercover Flex Tonneau for $670 with free shipping. I had to use their "Name Your Own Price" button to get it lower than the advertised sale price of $821.
For a 2013 DCSB the part # is UND-FX41002
Today i tried again and the lowest I could get it was $705 so YMMV but felt it was worth sharing for anyone waiting for a "sale" on these tonneaus.
Very pleased with the quality of the tonneau. They have made some improvements as it seems that some of the issues in other reviews on TW aren't present with mine (bolts marring surface, rough edges that needed to be sanded etc).
Very pleased with the purchased and 4wheelonline shipped it very quickly.