But that costs money :,(

Sometimes you want to keep ALL the energy out. The films also act to trap thermal energy in too.

I've personally used superfoil, it keeps all the light energy out. 42°C outside, in a double glazed UK home, and I still didn't need the Aircon until mid afternoon.

Depends on the country. Look for Gila window film. It's expensive, but paid for itself in one summer.

Any link to one of these? Not sure what to look for.