Level 5 !!!!!
I had wondered if sales would slow when it made it to level 4 and thus cost more, but buyers are obviously not deterred by higher levels if the image suits their needs. Likewise the percentage of subscription sales to credit sales has not really changed much either. I really appreciate having those subscription sales, as they help you to reach the next level where the credit sales earn you even more. And for those who have yet to experience an image reaching the higher levels, I will tell you... it is very exciting to get $4-5 or more per download on a regular basis!
Photo credits: Teekaygee.