Originally Posted by Rosemary Fryth
You are only locked into Amazon if you go KDP Select and that contract is only for three months, after that you can opt out and offer your eBook titles at other outlets including selling copies yourself from your own website.
If you're selling 75% or more of your copies through the Kindle, then you're "locked in", irrespective of whether it's available elsewhere. The majority of your audience is on Kindle. And if amazon drop their royalty percentage, then the majority of your earnings vanish overnight.