There is no way at this time to know if an increase of sales is directly related to offering DC as a payment option on your shop. It's the default payment method set by Etsy so unless the customer manually chooses to pay using paypal, any sale you make will route to DC, thereby giving an artificial inflation of the numbers.
At this time, you can't search on Etsy for shops who are accepting it vs. shops that aren't, so there is no way to tell for sure that you wouldn't have made the sale otherwise. The buyer doesn't even know DC is a payment option until they click on the item in search and then scroll all the way to the bottom or until they add the item to the cart. (Which is probably more likely since half the time buyers don't even bother to read the entire description all the way through. LOL)
Let's take hand stamped jewelry for example. 80 bajillon people sell it on here. It would be ridiculous to think that customers are finding items they love, adding them to their carts, proceeding to checkout and then dumping the item from their carts if you don't accept DC to search for a shop that offers something similar and does accept it. If you search hand stamped mothers necklace over 14,000 hits come up. A buyer is not clicking through tons of listings to see who accepts DC and who doesn't. So really, until you can somehow search by payment method offered there would be no way to tell how many buyers actually prefer using it to another method, know what I mean?
