The whole toilet seat thing is as misunderstood. If the Air force needs a new toilet seat for one of it's jets, and that jet isn't in production anymore, and you can't just go to homedepot for aircraft parts, then you have to order a bespoke seat.
Now setting up the tooling for an injection molded plastic seat, only to produce a limited run, maybe in the dozens, $10,000 per seat is a reasonable price.
I'm sure the Pentagon buys toilet seats at the regular price. The interesting thing about Pentagon bathrooms is that it has double the number it needs because of segregation.
There also the fact that the government has to buy domestic as much as possible. Not to say they don't use corruption to transfer wealth via those contracts.
In fairness, they can't just pop down to the hardware store and use one of those soap dispensers, since the changes in air pressure at altitude would cause them to leak all their contents or pop.
The average dispenser is basically two one-way valves, and a flexible tube you compress to squeeze it out (or a bottle with a pump). Everything inside would be forced out by the lower air pressure.
They barely ever do. Only when landing to an airport at sea level.
Upon take off, the cabin pressure is gradually increased until the regulatory 8000 ft, which is maintained majority of the flight.
You experience the same pressure changes while driving in the mountains, with the good ol' ear popping.