As a non-attorney that has also used PACER, I don't think of it in quite these terms. Sure maybe there's some level of public subsidy by making it free, but like you say, relative to the legal profession that subsidy per lawyer is at the noise floor. On the other hand, the value of making it free to people outside the legal profession is well worth the degree to which we'd be subsidizing the people in it.
For example, journalists. There's enormous investigative journalism value in the documents that have been filed in court. People say all sorts of shit in affidavits which turns out to be relevant outside the context they intended it for. PACER should be free, if nothing else than for the public interest value of its content (outside as well as inside the court).
Right, but I fixate on the fact that we could easily solve the journalism problem without making it free. Just raise the free tier cap.
Making PACER entirely free is regressive, absent some new scheme to single out the lawyers (like a dedicated lawyer tax or something, which runs into constitutional problems.)