It's the Black Sports edition is what he said. He said he also has some boxed (not sure about sealed) Sega CDs, Atari Jaguar NiB and a shitload of games for each. I don't know how to respond, because pricing this stuff is a small headache.
The sports bundles are probably the least valuable DCs. A NiB Jaguar would fall in the same range as a DC. Sega CDs consoles come in four different varieties: the CDX or JVC X'eye models are the goods ones while the Model 1 (goes under the Genesis) and Model 2 (side-by-side with the Genesis) have lots of reliability issues. Only the X'eye and CDX are worth a decent amount ($150-ish for just the system, controller and hook-ups).
The games are what will make or break this deal. I would ask him for a list, and then use VGPC to compare game values for both his list and yours. VGPC lists can be broken down by highest to lowest, which should help speed things up. I know you said you did a conservative estimate of your games, but it never hurts to re-check, in case you missed a gem in there.
I didn't see this mentioned yet, but are the games complete? A complete game can drastically improve the price of a game, especially for old titles (sometimes 3-4x).
You can ignore some games based on these general rules: a) sports games are almost never valuable minus a few exceptions, b) popular games (Call of Duty, Halo, Sonic, etc.) are pretty much guaranteed to never be valuable, c) popular games that are brand new might be valuable, and d) generally, RPGs hold their value better than most other genres, and you could probably add survival horror to this category.
That probably doesn't help much but it's hard to gauge these things without being there.