My best guess is that the coaster companies who design the coaster design & factor in the whole enchlata...
Why?
It's part of the themeing. It's part of the ride. It's part of the experience. When a Amusement Park turns to a coaster company to design a rollercoaster, they usually come up with an architect's sketch of the coaster which usually includes the queue, landscaping, & themeing. This is now-a-days inputted into the computer for a computer rendering & animation how it will look like.
They have to factor in the trees, the queue, and themeing around the coaster as part of the coaster's final look. If that isn't done, chaos envokes and things can be messy (because if a park decides what goes where after a custom coaster is designed, it most likely won't look right).
When a park says it has "Invested 12 million on it's new super coaster"...
That means that they invested 12 million on everything there... the concrete, the pavement, the trees, dirt, water... etc. As well as the rollercoaster itself (as for labor costs, I am not sure).
Of course, this is just a hypothesis... but my hypothesis' tend to be right 51% of the time