I'll take a stab... I'm not a collector of the 1891 single-shots but have always wanted one and watch their prices. Of the first three photos, a 1st, 2nd, and 3rd model...it appears the 1st and 3rd have original serial matching boxes and the second model has a spare barrel but no box? Based upon condition and box/spare barrel you're looking at $1,500-2,000 for each one in my opinion. I think $1,500 is conservative and $2000 is more retail but given their condition they may go higher. I would expect to get a price break for buying them all together in spite of it being a complete collection. I have no clue with regards to the cased multi-barrel set. It appears to include a .22, .32, and .38 barrel... and one Pope barrel? I think I see a pre-war SAT in there too. $4,000-5,000. So $8,500-11,000???? I would think that something in the middle would be reasonable for both parties. Like others have said, where else would you have the opportunity to build/complete a collection at once like this... personal inspection, no shipping/transfers, no sales tax or auction fees??? lots of variables a collector can add in or subtract. Good job for snagging the 4th model though... in my opinion the best purchase and most valuable item available regardless of what you paid.