This. Adwords is a tricky beast. Inexperienced people could easily be missing on 90% or more of targeted potential traffic.
Setting up an Adwords campaign to efficiently target the right people for a known product is a time-consuming project in itself. If you’ve never done it before it can take months to get right (and even if you’re experienced, it’s still a process).
Personally I wouldn’t put too much weight on the results of an adwords campaign.
There is also the question of the landing pages. These are typically optimized over weeks or months. A small mistake, the wrong choice of words can kill your conversion rate.
If you get crappy results from an unoptimized adwords campaign and an unoptimized landing page, what have you proved exactly? Is it the product? Is it the price? Or is it the fact that your marketing campaign isn’t there yet?