For Playmaker it is 3rd party pricing however, they are charging based on how much they think is fair for the time they put into it rather than a thought out price for a game maker.
You can't really compare the 2 though anyway in my opinion, they are not really the same as this is like a optional helper tool. Basically some of the plugins for Unity are almost like game makers or design programs themselves as they are so advanced.
This is not the only thing like that either there is other addons that make things simple with less coding like Vizio and Strumpy Shader Editor. Then a load of tools to edit scenes/maps etc simply, and there is now new addons released all the time.
I know i might get negative feedback for this comment but in my opinion Unity is on another level compared to Construct. Maybe a few years down the line Construct 2 might be able to match it though when it is more complete and professional, right now it only allows 2D though but Unity allows 3D also and soon flash exporting and then probably other formats in the future.