Every time you mention ceramic bowls an pump out tanks and £1,000+ and £100's on maintenance you sound more and more desperate. You are over egging it.
e.g. I'm a liveaboard and have a cassette toilet and spare cassette that was on the boat when I bought it 5 years ago. So far it's cost £0 to maintain and £0 to empty it. Your £100 home made bog seems expensive to me. I suspect anyone with a cassette toilet is laughing at your attempts to justify your choice on cost. You tip your pee god knows where, put your poo in dog bins? Street waste bins? because there is no "green" way for you to deal with it and your toilet cost you a comparative fortune. Cassettes, even flushing ones use almost zero water so you can't win there either.
You're loosing the argument on all fronts, in fact I suggest you get a cassette toilet so at least you'll be able to stop dumping your piss and shit in the local environment. No need to thank me.