They do enforce their cut on in-app purchase but since you can sideload app I see it at less of an issue (suppose all games would become free with a 40e in game purchase otherwise).
Edit: on the price parity while the policy might be listed as applying only for Steam key it's possible they engage in anti competitive practice since :
- does not control the OS and prevent you to install app outside of it (even on steamdeck)
- d̶o̶e̶s̶ ̶n̶o̶t̶ ̶f̶o̶r̶c̶e̶ ̶y̶o̶u̶ ̶t̶o̶ ̶p̶r̶i̶c̶e̶ ̶m̶a̶t̶c̶h̶ ̶o̶n̶ ̶d̶i̶f̶f̶e̶r̶e̶n̶t̶ ̶p̶l̶a̶t̶f̶o̶r̶m̶ ̶i̶f̶ ̶y̶o̶u̶ ̶w̶a̶n̶t̶ ̶t̶o̶ ̶p̶a̶s̶s̶ ̶t̶h̶e̶ ̶c̶o̶s̶t̶ ̶t̶o̶ ̶t̶h̶e̶ ̶c̶u̶s̶t̶o̶m̶e̶r̶ ̶(̶t̶h̶e̶r̶e̶ ̶i̶s̶ ̶a̶ ̶"̶P̶r̶i̶c̶e̶ ̶P̶a̶r̶i̶t̶y̶ ̶R̶u̶l̶e̶"̶ ̶b̶u̶t̶ ̶o̶n̶l̶y̶ ̶f̶o̶r̶ ̶s̶t̶e̶a̶m̶ ̶k̶e̶y̶s̶)̶.̶
They do enforce their cut on in-app purchase but since you can sideload app I see it at less of an issue (suppose all games would become free with a 40e in game purchase otherwise).
Edit: on the price parity while the policy might be listed as applying only for Steam key it's possible they engage in anti competitive practice since :
- http://blog.wolfire.com/2021/05/Regarding-the-Valve-class-ac...
- https://www.ign.com/articles/valve-ceo-gabe-newell-ordered-t...