Not really. They usually come from the fact that legal services are just exceptionally expensive. This, in turn, is largely driven by the fact that, for companies with a lot of money and a lot at stake, legal services are also exceptionally valuable. This drives up rates across the entire industry.
There are other dynamics as well, but I think this one dominates.
Also, you didn't answer the question as asked. If the goal is "file motion telling judge 'patent is not valid' without doing literally anything else", what exactly is the money spent on?
And I meant to give an earnest answer! If you are the defendant in a relatively simple patent case, where the patent is clearly invalid, the right procedural move is probably a motion to dismiss, which could come right at the beginning of the litigation. But merely drafting that motion will be costly, simply due to the cost of legal services.
EDIT: Of course, it often is not actually clear whether a patent is valid and enforceable or not. This could require evidence from experts about obviousness, prior art, etc. Assembling all of this in a way that is fair to both sides, and presenting it to the court in a way that is clear and compelling, is difficult, as one might expect. So this idealized situation may not be too common.
EDIT 2: In case it's not obvious, this shouldn't be taken as legal advice. Every situation is different, so you should hire yourself a lawyer, and not act based on general ruminations you read on the Internet by people like me. I am not your lawyer.
Ok, i guess you simply underestimated just how little the layman knows. :D
> drafting that motion
I'm going by this particular case, where the patent is obvious and patent bullshit. I would imagine that here a motion would be a form letter that could be handled in less than an hour? (Going by experiences in the german law system where i've seen a form letter to an unpaying client go out, cost and take effect, for half an hour billed.)
And yeah, in other cases it may be less obvious. I'm only talking about the case at hand, and other similar ones, where the patent can be seen to be invalid by anyone with good high school education and above.
Heck, shouldn't it be possible to informally request from the judge to say whether he already sees the patent is bullshit or not?
Whether you want to just rely on a short letter is, I guess, a matter of your appetite for risk. Ideally you would at least provide some argument about why the patent is unenforceable. (In fact, most jurisdictions have rules that require this sort of explanation.) And this would be framed knowing that the other side will have potentially very talented lawyers arguing that it is enforceable.
Since you don't get to file an unlimited number of motions to dismiss on the same topic (for obvious reasons), most litigants find that they want to put a substantial amount of effort into making their case as persuasive as possible before a judge sees it, even if the matter is fairly straightforward. It's the lawyer's job to help the client understand these levels of risk, and the client's job to decide how much money he wants to spend, given those risks.
There are other dynamics as well, but I think this one dominates.