If you plan on flipping a SE/30 on ebay then going to ebay and looking over ended auctions will give you a clue about its recent value ( that is what we do). If you were a mac user from back in the SE/30 era you would know about any add-ons to the unit and what they cost back then. Anything that enhanced the user experience back then will probably add value to it today. With a degree in economics I figure you know a little about how volatile the collectable markets are during high unemployment (buyers market).

People tend to get jumpy here when somebody joins and asks about what something is worth and then vanishes, the people here have a decent amount of knowledge about these old machines and tend to not like being a free apparaisal service (especially when you don't give them first crack at buying the items).