Valve

6.3.2 Sharing of Revenues from Workshop Contribution Sales. Unless otherwise agreed between the parties, and notwithstanding Section 6.1, Valve will pay Company a share of Adjusted Gross Revenues derived from any sales of Workshop Contributions that occur on a Workshop page specific to a Company Application or within a Company Application. Unless a different revenue-sharing arrangement is agreed to by the parties, Company’s revenue share shall be equal to seventy percent (70%) of Adjusted Gross Revenues, less a percentage to be paid to the contributor(s) that submitted the Workshop Contribution (“Contributor”). Valve may provide Company with the means to set or change the percentage paid to Contributors, and/or the allocation of the contributor percentage amongst contributors in cases of bundled item sales. If no percentage is specified by Company, the default percentage shall be twenty-five percent (25%) of Adjusted Gross Revenues.

The above is from the Steam SDA, a contract all new developers sign. The reports that valve takes more then 5% are false.