Surely you can work with Ebay to find a way to capture these sales without violating some agreement. It would be in Ebay's advantage to have a complete set of data.
Just took a random sampling of the last 200 completed items with SGC in the title and priced between $50 and $150. 75 items did not sell, 93 items sold via auction and were recorded by VCP, and 32 items sold via stores and will not be picked up by VCP. That's roughly 25% of completed sales from a small window sample (SGC cards between $50-$150).
Here are some specific examples that are not recorded in VCP and speak to the need for changing the business model:
http://cgi.ebay.com/1911-T205-Charle...item334abe5027
T205 Phillippe: sale price $155
VCP Average for PSA 5: $76.50 (last sale 6/13/10)
http://cgi.ebay.com/1910-E96-Phila-C...item1e5c8bba2b
E96 Konetchy: sale price $90
VCP average: $71.67 (last sale 2007)
http://cgi.ebay.com/1921-E121-80-Car...item563c68832b
E121 Collins: sale price $275
VCP Average: $225 (last sale 2009)
http://cgi.ebay.com/1910-T206-Ty-Cob...item335a065d94
T206 Cobb Bat On: sale price $800
VCP Average: $438 (last sale 2008)
http://cgi.ebay.com/1910-E91-C-A-Car...item2c54886a72
E91 Wagner: sale price $800
VCP Average: $492.20 (last sale 2007)
http://cgi.ebay.com/1911-T205-Fred-C...item5883805f9f
T205 Clarke: sale price $140
VCP Average: $100.25 (last sale 2009)
http://cgi.ebay.com/1909-1911-T206-T...item2ead128d34
T206 Cobb Red: sale price $580
VCP Average: $457 (last sale 2009)
http://cgi.ebay.com/1934-1936-Diamon...item2ea9c1a03b
1935 Diamond Star Hornsby: sale price $225
VCP Average: $133.50 (last sale 2009)
http://cgi.ebay.com/E94-Napoleon-Laj...item4ceff1b638
E94 Lajoie: sale price $1150
VCP Average: no sale history in SGC 30 or PSA 2