This is the 11385th most frequent Spanish word.
estratosférica
Extremely high or extraordinary; related to the stratosphere.
Here, 'estratosférica' is used as an adjective related to the stratosphere, indicating a region of the atmosphere.
La temperatura en la atmósfera estratosférica disminuye con la altitud.
The temperature in the stratospheric atmosphere decreases with altitude.
In this sentence, 'estratosférico' metaphorically describes an extremely high cost, akin to reaching the stratosphere.
El costo de la construcción de este edificio ha sido estratosférico.
The cost of building this structure has been stratospheric.
Here, 'estratosféricas' figuratively qualifies the ideas as being elevated or ambitious, like they exist in the stratosphere.