I agree it would be excellent to have a compilation of 7"es. I have quite a few, but I would spin them sooner if I had them on a single compilation. That said, there is a bootleg compilation CDr that has Audio Shock, Mother Fellatio, YTB, Night and Senzuri Monkey Metal Action, which combines a few in this fashion. Picked it up a while ago.
Also, yes, it's usually the CDs that fetch the crazier prices and which have become generally harder to come by. There's a couple of vinyl releases that you generally will have to pay out the ass for (Senzuri Champion, of course, but also some 7"es like Yasukuni Jinja), but other than that you can pick up most vinyl for pretty cheap. It's discs like Tokyo Anal Dynamite and Instruments Disorder that are usually pretty expensive.
It'd be cool to have a compilation of 7"es, and additionally some fancy reissues of all the albums. I would love to get good, official copies of the few things I'm missing. Also, it would be really great if there could be a compilation of sorts that featured tracks from comps or rare/one-off tapes. For that last category, I'm thinking of sought-after gems like Piano River, Public Environment, the live demo, and the split with Masonna, though for some of these it will probably be hard to get a hand on the source material at all - even if someone had the intention of reissuing this sort of stuff, it would still be a difficult task. Still, that would be the dream though.