If the SEO work (on-page or off-page) is understood to be one-off, with the work itemized as in the above post, with no requirement for a "guaranteed ranking" result, charging in the low hundreds seems fair. The MOZ study I cited quoted $1000 as the LOW end set price for a one-time work SEO project, or $250/month ON UP for ongoing work as the standard industry prices.
This is then the real floor for normal pricing of standard SEO work on a site, which can then be modified up or down based on details that make a particular case non-standard. The buyer (in light of this market price range, established from a review of 500 SEO providers) should not be in a position to low-ball from the start to say "$75, that's all," but should reasonably negotiate the fee based on the details. If the buyer insists on a "guaranteed result" (basically, demanding a refund if the site doesn't rank) they should definitely pay on the higher end of the scale---i.e., a thousand or more, not hundreds---to justify and properly reward the risk they are forcing onto the SEO provider.
