It's actually very smart to do it the way you are doing it. We do this all the time and have tested it extensively. What you want to do is to see if your ad is getting enough "reach" at the 20 cent click level. Reach is the amount of times your ad is shown.

If there aren't many others bidding, you can bid pretty low and still get lots of reach. However, if your ad isn't getting shown much, you'll know that you should raise your ad price.

Make sure you also test using Optimized CPM versus paying for clicks as well.

Hope that helps.