I came across this article
It looks like it cost 40k to submit a patch to be certified.
I also came across this http://multiplayerblog.mtv.com/2009/03/20/sony-now-charging-publishers-for-ps3-downloadable-content/
Sony charges 16 cents per GB downloaded content through PSN.
So if TWD update is 1GB exact and downloaded by 1 million customers the cost to TTG is 160,000 for the content downloaded over PSN.
Thought it was just a interesting fact.