Do you mean the Gyraf G7 microphone?
As far as cost, I've been doing some looking into it, assuming I would buy top-notch components (Telefunken tubes for $55 a piece, a John Peluso capsule at $150 a piece, etc.) I end up at about $450-500 or so per mic, which is a very rough guess. It need not be that much, though, since you can use cheaper capsules and tubes to good effect.
As far as other mic designs, there are many threads around on modding existing cheap condensors. Give them a look. :thumb: