I find great.
This will encourage developers to add steam workshop and will encourage better mods and for them to be updated.
Is win win for everyone.
But some modder are asking for ridiculous prices, we will have to wait for the prices to balance it out the the increase in quality and support due to financial incentive start to appear.
Edit:
Just learned mode developers earn only 25%, if you account for the 30% tax it goes down to less than 20% from revenue.
Steam is being greedy.