www.modacar.com has them for $499. I have never purchased from them before so don't know their service level.
MugenCivic480 was trying to organize a group buy for Koni yellows for significantly less but unfortunately I haven't heard anything about that for a while. I would recommend that you PM him to check on availability.
I know this is a little OT but do the threads on (GC) coilovers get gunked up in winter time due to salt?
Gordon.