I have several Katanas, a Scimitar, A high quality short sword, a claymore, a cutlass, a saber and a rapier. Most swords (especially katanas) on the market are cheap Stainless Steel made in pakistan/taiwann/spain crap, average retail about $135.00 US. A good katana is made of Carbon Steel* full tang and folded at least 8 times (though a thousand fold katana would be far better) and retails between one and eight thousand dollars U.S. Honestly though, they aren't great for defense as the Katana is not what you see in animes. A katana is meant to be used as an up close cleaving weapon, requiring inefficient muscle mass and expenditure of energy. I prefer my rapier, it's light weight, long range and lethal with only a little bit of practice as regards to accuracy. Not to mention finding good fencing lessons is far easier than good Kendo in the U.S.
*There is some debate about which material is better for swords. The answer depends on what you want the sword for. A Carbon Steel Sword will rust without care, but it holds its edge and sharpness and is generally a very tough blade. Stainless Steel is pretty, won't rust, but the blade is brittle, dulling after only light contact. Made for Display.