Ha... 4x5 films gets you great and detailed pictures, but, as you say, one must be either rich or shoot with great care :-) Sped graphics and Busch Pressman can be bought "almost" new at the Bièvres Photo Fair near Paris, every year in the first WE of June. People gather form all over Europe and even from Japan... :-)
I would like to use these cameras with a cheapo 4x5 qinch chip setup. That way each pixel could be 50µm x 50µm and we still get a lot of resolution plus all the DR and Speed we could ever wish for.
lets see:
4 x 5 is 102mm x 127mm and with 50µm-Piuxels we get 20 per mm, so the resolution would be 2040 x 2540 qpixels. no, not enough
then lets take 20µm-pixels, which makes for 5100 x 6350 qpixels ... much better
We can use all the old low res 4x5 glass with that setup, even the wide angles!