other than the "uber" collectibles (where they seem to know where 99% of all that were ever built are/were), its hard to know the "rarity" of "regular" cars like this Pontiac .
But the GM cop car guys tell me the Pontiac 'Enforcer" coupes remaining can be counted on one hand. you never know what's in somebody's barn that will turn up later today.
Is the picture of the oneon ebay a few years ago? I remember that car and cannot remember what it went for but I did ask him questions. Look on youtube for a gold 1977 pontiac LeMans squad video. It was chasing a Trans Am if I remember correctly at a Hot Rod meet like show. I seen that car in Wisconsin, it is a tribute car and getting alitlle rough around the edges. The motor looked like a Hot Rod type, not close to period correct. I was not impressed. Goofy sayings on it also.