How to choose from expired traffic domains?

I do domains but not SEO. I buy and sell based on the merit of the name itself. I tried domain parking in the past briefly but concluded it was useless.

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However, there are people who profit off of it.

How does one go about choosing a domain anyway? I see the auctions, one is at $3500, the next one is at $25, although I can't tell the difference on the surface because both have got backlinks, referring domains, and both get ''traffic''.

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Can anybody enlighten me?