+1. Judicious use of sales technique definitely helps pitch the content better, but one can easily go overboard. IMHO, the analogy actually goes in the other direction, where one aspect of sales is trying to convey some information in an effective manner. Beyond that, sales is (often) partial in a manner antithetical to teaching (such as inducing a particular decision), whereas good teaching aims to induce enough engagement to make listeners think for themselves, and then help them along the way.

When teaching (as in sales), there is definitely such a thing as overselling.