sbrettoncm - 11:34 am on Dec 18, 2012 (gmt 0)
Samples are meant for trial purposes. So I don't think your consumers will like it if you start charging for samples.
If you are worried about your earnings, then you need to convince your consumers in a way that they use the sample, and immediately make a purchase decision. Don't give them a lag time between trial and purchase. The quicker this process, the faster your sales figures will increase.