Smashwords does an annual survey of indie publishers results and this year's has some interesting revelations. You can read their blog here: http://blog.smashwords.com/2017/06/smashwords-survey-2017.html
And view the results of the survey in a slideshare here:
Significantly, they found signs that many indies who are selling ebooks well at $2.99 should probably experiment with higher prices. In previous surveys, $2.99 and $3.99 were the sweets spots. It looks like it's time to add $4.99 to that mix.