the ebay auction are gm repros for sure. the ones pictured on the left are the real originals, the ones on the right are the ones gm made available for purchase later on. i think this is a case of what brett described awhile ago on a thread about "true" nos items vs repro nos items. yes the ones on ebay are gm parts, but they are clearly NOT the originals pictured on the left in the above pics.
also, repros are not plastic, they are metal. but most improtant of all, the prices in the big company catalouges are way overpriced... they gotta make a profit on each part they sell. like brett said, he can get originals for $99/pair! & $175 for a used set of emblems is not what you can base realistic prices on? heck, i got a set of these & i could ask $250... doesn't mean one can base their price on that exagerated price.
& while gm stuff does seem to be kind of pricey lately, these can be ordered direct from gmpartsdirect.com for about $80 each, that just shows how much the big guys mark them up.