It's worth the $. We replaced 33 (yes, 33) windows on our 1982 contemporary home with 4 levels. All odd shapes and the house is not that well insulated. The savings on our energy bills have been enormous. Even on days when it is close to 100 degrees, our AC does not go on until at least noon time. It's much warmer in the winter, too. Before, we had issues with some rooms being freezing and some being too hot and that's gone away.
I have learned in home repairs, yes, you should get several estimates, but generally, you get what you pay for. Obviously, previous owners of my house did not subscribe to this theory.
2015 Trek Silque SSL
Specialized Oura
2011 Guru Praemio
Specialized Oura
2017 Specialized Ariel Sport