Did you consider "Free" as ONE OF the amounts in the field? That could conceivably have given you the extent of the gap between "Free" and "Paid" for your product. You could have used the data to figure out your the correct price points.

I'm sure most hackers in this discussion have heard of the famous article by Fred Wilson 3 years ago, but here it is anyway: http://redeye.firstround.com/2007/03/the_first_penny.html