We're using it when compiling our code, but our software deliveries are bundled with the amazon Corretto (because we already have a contract with Amazon because of AWS, so getting security updates shouldn't be an issue) and our installer offer the option to use another JRE, so our clients can use any JRE 11; but for Oracle 11 JRE, they'll have to pay Oracle themselves.
To answer the OP, we didn't rewrite anything, just switched to a no-cost JRE. And since we did it at the same time of the Java 8 -> 11 switch, there were no extra dev costs.