>taxes, payments

The market rate for this is low single digit percents.

>update distributions

Bandwidth is not worth a percentage of game revenue. If it were it would be <1%.

>DRM

Steam's DRM is terrible.

>anti-cheat

Also terrible.

>user management...

This is not worth a percentage of revenue.

All of these together is not worth 30%. The only thing worth 30% is the ability for the Stram store to put your game in front of a random person. Being able to reach new customers.