When things cost as close as possible to their MARGINAL cost. The marginal cost of mailing a letter is very low, almost certainly closer to $0 than $0.83, especially if you accept letter carriers have to run their route every day regardless.

The problem of course is the USPS has enormous fixed costs, including I would argue the pensions (honestly not sure how they would be accounted for in a GAAP sense, I'm absolutely not an accountant)

Federal funding has long distinguished between the two for other things like transit. You're only allowed to use federal funds for capital expenses, not operational expenses. USPS getting a taxpayer subsidy for their fixed costs doesn't seem that nuts.

I think I've received two letters in the last year. I haven't received any individual junk mail letters.

The letter volume last year was 90M for 6M people, so about 15 each. I assume elderly people and others who have opted out of receiving government and business mail digitally drive that number up.

(Someone still delivers a bundle of leaflets from local businesses all together every month or so, and a local newspaper, but I don't think it's the postal service. Every home gets the same bundle.)

I personally get a massive benefit from USPS being cheap, despite the fact that I send no mail. It provides a massive low-cost physical delivery network across the country, with service to every address. This is a benefit to me because it makes business and personal communication simple and reliable. If I need it personally, it's there. If I don't, I still rely on thousands of parties who do.

Your position is like claiming the interstate system is useless because you don't have a car, ignoring how all those goods your life relies on actually get to you.