I just checked history and what I am seeing is this.....
This went for $650 but appears to be missing only hubs but it has an SR seat post....
http://www.ebay.com/itm/1984-Campagn...item1c1ef29dc7
This went for $635 and appears to be complete, even with pedals and seat post of some kind....
http://www.ebay.com/itm/Campagnolo-S...item415dde67c4
This one went for $935 and appears complete and includes skewers and a cassette....
http://www.ebay.com/itm/Campagnolo-S...item2a1437fdeb
This one went for $670 and is in fact missing hubs, bottom bracket, and headset and no seat post either......
http://www.ebay.com/itm/Campagnolo-1...item43a9712d80
This one went for $499 but is missing headset, downtube shifters, and brake levers, but has hubs with skewers and a seat post of some kind....
http://www.ebay.com/itm/CAMPAGNOLO-S...item336c7c7c21
This one fits the OP's case as it is missing hubs, headset, and bottom bracket, but it only sold for $500...
http://www.ebay.com/itm/Campagnolo-S...item43a99e7d44
I may have missed on some of the details about what's missing as I did this rather hurriedly, but the bottom line is this. If you think that you can throw a complete SR group on eBay and get $1000 and partials are solidly going for $650 to $700, think again. Besides that all of this is a hodge podge to begin with and consequently is very hard to support any definitive conclusions. They all seem to be missing different stuff, pedals and seat posts are a bit of a wild card, and of interest to me is the fact that almost all of these listings originated in Europe, so that needs to be evaluated as well as to whether that inflates, deflates or is irrelevant. And all that doesn't even take into account the vintage (what year is the group) of each group and how that plays into the demand. Lots of inconsistent data with inconsistent results on several groups, none of which contain the same exact items or are form the same time period. The only conclusion that I can draw from this is that partials go from roughly $500 to $650 and completes can reach into the $900s (one example) but more likely would go substantially lower. I think the OP has overstated his case by on average $100 to $150 and in the case of complete groups maybe more. The occassional listing that reaches his threshold is more the exception than the rule. There are more instances not reaching his numbers than do. And it is important to note that no two of these are alike so what it all comes down to is what you have (content), what it looks like (condition), when you list (who's bidding) and perhaps where you are (location). Maybe I should have mentioned that the alignment of the stars might be critical also. Go ahead, roll the dice!