Fallingwater is a proof of concept by a famous designer meant to push the medium's limits, and the builder's decisions to go against the design didn't help. The cost to repair is more representative of the value of art than of infrastructure.
Fallingwater is for sure a bit of an extreme example. $2m equivalent (+/i) to make, $11m to repair is a 5x jump. This is a difficult delicate job.
But I do expect concrete maintenance in many places is going to quickly reach & exceed initial build costs.