Symantec and Trend Micro are defending against an allegation from Intellectual Ventures that they owe it $310 million combined for a license to one of its patents. The pair are using a novel legal theory which points out that Intellectual Ventures only paid $750,000 for the patent and it could not possibly be worth as much as $310 million.
They are also using the traditional arguments that Symantec and Trend Micro do not violate IV's patents in the first place, but the “it is not worth it” defence could seriously scuttle the patent troll business, if it is accepted. If the royalty is capped at the purchase price, there's obviously no point in being a patent troll as you can’t really charge more for the licence than you paid for it. In this case the most that it could collect from the security companies is $750,000 each.
Symantec and Trend Micro lawyers argued that the law prohibits IV from calculating a high royalty. A patent license is, by definition, less valuable than outright ownership of a patent, Symantec and Trend Micro lawyers pointed out.