Well you can continue to replace parts until you've repaired it, or get a volt/ohm meter and a circuit diagram. Then logically trace the circuit until the problem is found. since you didn't say what kind of car and year it makes it difficult.

most imported cars have a four bulb system. the brake lights are separate from turn signals. American cars interrupt the brake light and make it flash on that side. so American cars route the wiring through the turn signal switch. a bad T/S switch will cause no brake lights but T/S still works.

does the circuit actually have power? ground?

It sounds to me the money, time and aggravation already spent would have paid a diagnostic fee at a reliable shop. One can always decline the repair since one only asked for diagnosis and price quote in first place.

Some cars power the brake lights through the body control module or GEM module. Other cars switch the power directly. You apparently think all cars are wired exactly the same and didn't provide critical info like, year, make, model. Try again and you'll get a better answer.

Pull out your owners manual, there will be a list of what each fuse and relay does, since you checked the fuses the next step is relays, find the one for your brake lights, and pop a different relay from a working component in there (a/c, fan, headlights, it doesn't matter for a short test). Have you checked the fuses in the engine bay? or if it's a caddy in the trunk as well. Get you manual out, find everything (fuse/relay) related to brakes and check them.

Make a fist and pound the dashboard several times. Maybe it is a floating wire.

Brake lights are not needed, which is WHY you learned "hand signals when studying for your driver's exam. They work. Day or night.

I have changed all light bulbs and checked all fuses behind glovebox. I have replaced the brake light switch at the pedal. I do have reverse lights and turn signals. Still no brake lights.