Like Steve, I use Adwords daily and we get the traffic and conversions. These are niche conversions, not a general conversion like going after the word "web hosting".
Your adwords need to target a specific page within your site, not your main page. Those pages must have a high Qual Score too (adword relevance). The higher the relevance, the lower you'll actually spend for your click.
We run one particular campaign we're running this month. So far, we're running at 0.45% click-through rate (28 clicks out of the 6,240 impressions). Average position is at 6.59 and we're converting without issue.
The purpose of the adwords campaign is not to just drive traffic, but to drive targeted traffic. By narrowing down our clicks to only 28 clicks, those are 28 people that are truly interested in what we have to say. While we can spend more money and move higher in the positions, the intended target would also change.
You may have been targeting the wrong audience, wrong time, wrong day of the week etc. We turn off our campaigns during certain hours, and flood it at other times. If the person you're hiring is doing this for a living, and was able to drive traffic to your site, and you still got limited conversions, then there's something wrong with your sales funnel.
Have you evaluated where the client bailed out of the sales funnel?