I've "built" several compact cranks, using a Sugino double with 110 spacing, and then "borrowing" the two largest rings from a MTB triple. Visit a few co ops and you will likely find some good candidates.
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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.