If you have a pile of parts, rebuild that Trek and get your money back just for it. I will sometimes save a decent MTB frame (respected brand), and then convert a not so respected brand donor into a Trek. As long as the parts are comparable quality, it can be a reasonable project.
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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.