That's such a broad question. It would help a lot if you put together a list of 10-15 (or less) sours you want and we can give you quick feedback on each one.
1:1 you could probably get Almanac sours, mid level Lost Abbey, Allagash shelf stuff, etc 3:2 some NG larger format fruit stuff, shelf Jester Kings, Standard Russian Rivers etc 4:1 Harder to find Jester King, small format Allagsh, maybe a Coolship to the right person, some Cantillons, possibly some mid-tier Russian River, Upland, Cascade (price on these is just too high to go any lower). Though anyone trading a beer of this value is probably already flush with BCBS. Not happening: Harder to find Cantillons, Hard to find Russian Rivers You'd be better served to find a couple of local harder to find beers and try to do a multi-bottle trade. Maybe 2 BCBS + 6 other local brewery-only beers, east coast barrel aged stuff, etc.
