Hi Jorge,
As for charging: only way to know is to bid too high, lose the job; then ratchet down until you get the job.
But imho, you should stop wasting your time producing ads for local dealerships.
Concentrate on the beauty shots which we all probably thought were stock footage, because they looked great (and far better, to be honest, than the car dealership shots).
You could probably monetize the beauty shots by selling yourself as a go-to person for Caribbean timelapse/stock shots. And you’d have more fun.
If you want to broaden your skills to learn how to make an ugly car dealership interior look beautiful and appealing, that’s your choice. But (a) that’s actually pretty challenging; and (b) I bet there are a thousand directors who know how to do that, who would love to be creating that “stock footage” that you already do so well.
If you are absolutely determined to do commercials, try to integrate your unique talents more closely into the sales proposition, e.g. put a car and a model into a beautiful setting and shoot away. Avoid those ugly dealerships; they aren’t part of your soul.
Bob C