>>Are they worth the cost/tradeoffs?

Hell NO!!

Ubiquitous on-the-ground lighting is already disrupting plant, animal, and insect life cycles.

Adding a blanketing sun reflector illuminating five-plus square kilometers at a time will obliterate critical signals to everything living there, and won't do any good for the humans.

And nevrermind the astronomy.

It is an abomination and nothing but a scheme by amoral people to separate other fools from their money.