Nice, I may say
A very tricky move from Envato side. With that fixed author fee, you're strongly stopped to set a smaller price than a specific one.
Let's say on CodeCanyon, with $4 fixed Author Fee, if you set a lower price than $20 you will get less than now (70% of item price). So, will force all the authors to have a higher price than $20.
Most of the items from CodeCanyon are under $20. So if you keep the price, you will get less and Envato more. If you will increase the price then you you have big chances to have less sales because of the other items prices.
So, the only chance is that all items be aligned with a price starting with $20 (on CodeCaynon). All authors will understand and will accept that?!