Best place for me to find small obsolete parts is the co-op. I typically drop off a truckload of various left overs, pick up a few odds and ends. I just make sure the scale is heavily tilted in favor of the co-op. They have a file cabinet full of broken derailleurs, that can supply jockey wheels, fixing bolts, limit screws, or whatever.
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Please don't confuse ebay "asking" prices with "selling" prices. Many sellers never get their ask price. some are far from it. Value is determined once an item actually SELLS. Its easy enough to check SOLD prices.