You cash out by selling ISK on a website. Its called RMT and is forbidden. But many people do it anyway. They use bots or steal accounts so its not like they care about game anyway. Its all about cash for them.
Eh I forgot that RMT will be build in into chinese server tho, you will be able to sell ISK for cash there.
https://massivelyop.com/2018/10/04/dataminers-dig-up-eve-onlines-chinese-server-elements-rmt-interfaces-and-prison-sentences/