I've sold in to the low 5 figures for my products in the last year, and had less than 15 'refunds'. Actually, no *requests* for refunds at all, but a few cancellations via Google Checkout. A few purchase, then cancel 2 minutes later, and a few where the credit card was declined.
My price point is pretty low - $4.99 - which may account for some of it - perhaps people just don't think it's worth it to ask for a refund on that amount?
Or perhaps the market I'm serving - technical developers - made enough of a judgement call before purchasing to be satisfied with their purchase?
What are your return rates? What factors do you think play in to refunds/chargebacks, and what markets have high and low refund request rates.
What steps do you take to ensure fewer refunds?