you need to know the taipe of wall you have
maybe you can install a small window for arund 600$ to 800$

Here is a link that might be useful: general contractor los angeles

I'd definitely put in a couple of windows in the BR, one on either side that can catch the predominant breeze in your area. If you DIY you can do that for less than $400, depending on the size and type of window. You'd want something compatible with what you already have.

It would be cheaper than the doors to put in a window, true. We have siding so cutting through the wall is complicated. We put in a window in a windowless bedroom in the daylight basement and needed help to get the siding put back in order. What about the French doors? Ours has a single pane of glass in a wooden panel in each door. Instead of replacing the door, would it be hard to remove the glass and put in a window in its place that would open?

You could do that, though I think it would look a little strange going from the floor to 7' or so. Extra windows will definitely add to the value of your home.

How about screens for your French doors? There's several good retractable screens that keep the bugs out, and practically disappear when you close them. We have this model (below) for our front door, and it's also good for keeping cats inside.

Here is a link that might be useful: Retractable screen

I talked to my DH about adding a window and he said he would rather put in some kind of vent and a heat exchanger. He helped my son build one once for a science fair. He's not the one who has trouble sleeping from not enough fresh air. It would be OK with me if it works. We can't really leave the doors open in the winter for ventilation as too much heat would escape. A window could be opened just a crack. Besides, my plant shelves for starting seedlings are in front of the doors so we don't even use them at all.