It's already expensive, and I'm barely past the prototyping stage! My wife is resigned to the fact that we'll never have any money. But that's what happens when you marry a man with a plan!
The antennae will actually be 12m diameter "dishes", but at first I'll be leaving the outer 2m circumference unilluminated. If I'm able to cover the outer portion later ("able"="afford it") then I will.
Luckily I get a discount on metal through the company I work for, and most of the key engineering will be done for me at cost by their mechanical fitters. I'm a comms tech so have that side covered. Lots of keen volunteers in these departments looking for interesting projects to waste their time on!
It's the little things which help: I'm mounting the antennae on railroad bogies and track which I get mostly gratis courtesy of some of the railroad enthusiast employees at the company! They are ex-railways staff and also members of a local train society!
Pictures of the site will be up sometime soon...