At the end of last year Google changed the Android application refund time window to 15 minutes from the existing 24 hours. Since the change was put in place I have seen my (low, but acceptable for a niche application) 4-6 sales a day drop to 3-5 a week.
It is my opinion that Google's changes have made it significantly more difficult to sell applications on the Android market because people no longer "try out" applications that catch their eye, only purchasing applications they are absolutely sure will work.
Instead of complaining on the Google message boards, I have decided to release a free "Lite" version of Beat Dialer with only 5 samples.
It will be interesting to see whether this succeeds in enticing people into purchasing the "sample-packed" version or not - I'll certainly let you know.