The problem is threefold: the true marginal cost of a PACER page is closer to 0 than 10 cents; the fixed cost (building an electronic record system) is already paid by the public; and the complication of a price discrimination mechanism would drive up that marginal cost rather than capture true willingness to pay.
This trilemma shows up whenever we try to meter public goods in this fashion. We could, in theory, price public transit or water or what-have-you by evaluating willingness to pay and charging each person that value. However, in practice the invasive monitoring necessary to do so is an enormous burden. We can sort of spread this out with municipal services by (as you noted) replacing trunk lines/pipes with a general fund and asking individuals to pay for the last mile, but that mostly works because the real marginal cost is measurable and not near 0. Further, for utilities, the willingness to pay has good proxies: the end of the last mile is at a real house that isn’t going anywhere. For PACER I doubt that’s the case.
Again: PACER fees do not simply pay for the marginal cost of delivering a static file.
Right, but 1: We already pay for the fixed costs and 2: the real marginal cost--however you want to measure it--is still closer to 0 than 10 cents.
No, it pays for costs unrelated to serving static content. It's a use tax. The fees do not entirely have to do with paying for a website.
That’s right. And use taxes can and should be calibrated to not just collect money but achieve public policy objectives. If the real marginal cost were close to 10 cents a page, we might be able to argue that funding the system other ways would be more distortionary but it’s not. We have decided with lots of static file services (including Supreme Court opinions) that the right use tax is 0, because zero-cost access is a desirable quality in itself.