Medication is nothing more than a standard inhaler (~$25-35). You will need to get a special hand-held chambered device called an aerokat (~$40) that you press to your cat's face and spray the inhaler into so they actually receive the dosed amount. Dosage will be once every 12 or 24 hours, whatever is just enough to prevent the attacks. Works a treat. Oddly enough, the cat won't mind sticking an inhaler device over his face for a handful of seconds as long as you pet him at the same time.
Oh, and if you record the event happening, it makes diagnosis a lot quicker. It's pretty unmistakable.
Sorry I can't help with the diagnosis cost. Those can vary so wildly where I live. That and I totally forgot how much that was