Here is what I saw on auctions within the past 6-8
weeks (give or take a 1000 yen):

Original Settei (mostly incomplete sets)
Around 180 sheets:  50,000 yen
Around 60 sheets:  27,000
Around 34? sheets:  18000 yen

Gengas/Dougas
Around 34 sheets:  22,000 yen
Around 59 sheets:  8,000 yen
Around 34 sheets:  24,000 yen
Around 50 sheets:  22,000 yen
Around 150 sheets: 10,000 yen

Majority of these are of the same characters and
mostly on or around the same scenes.  The prices
seemed so varied that it is very hard to determine
their values and the sellers didn't show pictures
of ALL the sketches.  Is it possible for the
prices to fluctuate so much?
I did notice, however, that the prices for the
gengas/dougas did shoot up within the past 2 weeks
though (and I mean like 2-3 times more).  Maybe it
just suddenly got discovered or something.  Who
knows!!  *scratches head*

Star Phoenix