ah, but reputation matters here... you don't want to have a reputation for being easy money for patent trolls. Additionally, as google doesn't seem to be a patent troll, it's probably also in their interest to set legal precedents that weaken software patents.
I mean, obviously, this doesn't mean 'always fight' but it's another value you need to punch in to your equation, one weighing in on the 'fight' side.
In my business, a similar example would be the money I spend on running an aggressive abuse desk. Running a less-aggressive abuse desk would be cheaper, both in the work it takes and in customers I've lost, at least in the short term.
But in the long term, /because/ I have succeeded in making my service a hostile place for spammers, my abuse complaint rate is much lower than it would be otherwise. for a while, another VPS company rented a few servers from me... and in spite of being something like 1/60th of my size, they produced more abuse desk work than the rest of my customers combined. I believe, because I have an aggressive abuse desk.
(I mean, there are other costs... I've lost at least one legitimate customer I know of, because he was compromised and his box was spewing ssh attacks over the network. I shut him down with an email notice, the email went to the shut down box, so he never got it. )
my point is that there are real business reasons to fight that sometimes go beyond the immediate results of that fight.