Hey Matthew,
I've actually got some files for a custom full-hand ergodox tent with an adjustable angle parameter if you'd like. It's only for full-hand though, so you'd need to modify it in openscad for regular ergodox. Lemme know if your interested and I'll find the files.
There's no real way to do an estimate from a 3D model alone, because how much filament you use also depends on your infill settings as well as the model size. I'd say it's a super safe bet it'll be under $5 worth of filament.
Chris