First off, Cipro is the only oral (tablet form) antibiotic that has been approved to treat anthrax. Not too many people are going to go out and buy IV bottles with penicillin G.
Second off, it's incredibly fucking stupid to stockpile the stuff OR to self-medicate unless you REALLY know what you're doing.
1) Cipro degrades over time, like almost any drug -- if you get exposed next July, the stuff that's been sitting in your gunsafe isn't going to be as potent as the stuff you buy fresh, and that difference could kill you.
2) The specific strain of anthrax (or whatever other bacterial-DNA-based disease) could turn out to be resistant to Ciprofloxacin, in which case you'll be dead by the time you figure it out.
3) If you take the medication without really having a disease for which it would actually be needed/useful, such as treating a cold with antibiotics (the pinnacle of stupidity), all you do is kill off the non-resistant bacteria in your body, leaving your body filled with bacteria which are resistant to that drug -- and since bacteria swap DNA fragments (plasmids), if you do get infected with anthrax later, the anthrax bacteria can "learn" resistance to Cipro more quickly, at which point you're dead.
4) If you take it before you get tested, the test might come up negative, at which point you'll probably slack off -- which would allow the remaining, now-resistant, bacteria to reestablish themselves. Subsequent treatment would be futile, and you end up dead.
Not to put too fine a point on it, but does anyone notice how these all tend to end with "... you're dead"?
(#4 is basically what happened to me last year, except that it was the physician who fucked up by underprescribing the necessary antibiotics because his philosophy was to "help the body heal itself", rather than "to cure the illness". The resulting mess cost me eight months, several thousand dollars, my job, several more thousand dollars, and nearly my life. Q.E.D.)
Third off, there are plenty of companies out there that can make Cipro. The issue is royalty payments to Bayer for their patent. IMHO they deserve every penny, since if they don't make money, they don't develop new antibiotics. And we need new ones because the existing antibiotics are being rendered useless because stupid fucking morons go around abusing them -- underdosing themselves, taking the drugs when they're not needed, feeding them to factory-farmed animals to prevent disease, and all sorts of other really pathetically bad reasons.
If the above sounds preachy to you, just wait until you get one of the "superbugs" that are going around nowadays, and see how fast you get converted -- if you survive the experience. . . . Maybe your wife, children, or other heirs will get converted instead.