One of the wonderful things about the Internet: if you don't want to pay Amazon 30% there is a universe of people out there you can sell to for 3~5% or so through your own web presence. You just have to go get them.
This is because unless you agree to exclusivity, you will be denied access to essential marketing tools like free promotions (via the KDP program), which are essential for building initial social proof and give the book at chance to take off in rankings.
Unless you have a pre-existent audience that you can point to your Amazon non-exclusive book, there is zero chance that it will take off.