That doesn't change the fact that this isn't about cross-play like your original title suggested which is my point.
And this isn't about the userbase. It's gameplay hours. That would offset the gameplay share in favor of the platform with whales, wouldn't it?
They don't want their $/h to be at minimum 85% of the average (whatever you mean by average). The percentage of PSN revenue should be at least 85% of PSN gameplay share. Otherwise, the devs get charged a relatively small fee. The fee doesn't offset Sony's revenue to the point it becomes 85%. Not even close.
Userbase is gameplay hours. The main difference between whales and most users is not played hours (though they play a bit more) but money spent. And whales spent way more than their share of gameplay hours.
Regarding the Average PSrevenue share / PS gameplay share IS average :
(PSRevenue / Total Revenue) / (PS hours / Totalhours) > 0.85
We can recombine that equation to:
(PS Revenue / PS hours) / (Total Revenue / Total hours) > 0. 85
Which brings:
PS Revenue / PS hours > 0.85 * (Total Revenue / Total hours)
Which means:
PS Average $/h > 0.85 Average $/h.
The fee is set to be the nominal difference paid to Sony so that they get the equivalent of at least 85% of the average. The fee is "less" because while PS revenue then gets charged at 30%, the nominal fee gets charged at 100%.
For instance in the example:
PSN Revenue 600k, Nominal Fee= 52.5k -> Actual money to Sony is 600k*0.3+52.5k = 232.5k. If we raise it to the equivalent of "30% cut" (by dividing for 0.3) -> 775k in revenue... which is very much close to 950k (once you account the 85% -> 911k) they expected due to "gameplay share". Its a tool to ensure they are always at near minimum of 0.85x average $/h
Not average, in relation to the userbase.
Average $/h accounts for userbase. Thats what the "/h" does