With regards to the japanese sword being a one-shot weapon, I think you're referring to the mass produced swords (kazu-uchimono) for the lower ranking samurai and/or ashigaru. Higher quality blades by renowned smiths, while certainly not designed to cut through car engine blocks or oak trees (like ANY sword can do that, lol), are made to a higher standard.
With regards to higher quality blades, the koshirae AND the polish make up a substantial portion of the end price. You can put regular brass kodogu on a Howard Clark L6 and it'll still perform just as well. Never mind that uncoated brass tsuba, fuchi/kashira, menuki are ugly as sin and garish in the extreme. People don't want ugly fittings, and thus are willing to spend extraordinary amounts of cash on custom-made kodogu from master craftsmen. I'm guilty of that myself. I spent over $400 on a tsuba, fuchi/kashira, kojiri and menuki from Patrick Hastings, and that was just his basic, simple Higo work (but they're exactly what I like anyway). If you wanted nanako work, or carvings of dragons, waterfalls, and other themes, be prepared to fork out twice as much, if not more.
Then there's the issue of the saya. Good saya cost upwards of $200 USD, fully lacquered with horn kurigata and koiguchi, hand-carved to fit the blade perfectly (as opposed to commercial saya, which are one-size fits all).
Then there's the issue of the tsuka. $60 - $80 for a custom carved tsuka. $50 for the silk tsukaito. $75 for a high quality full wrap of samegawa. $60 - $100 for a really good wrap by an experienced tsukamakishi.
THEN there's the polishing - which can cost upwards of $60 USD an INCH of nagasa, for a sashikomi or kesho style polish by a master togishi. Most people opt for a tameshigiri polish, $25 - $30 an inch.
So be glad that you can get a relatively well-made kazu-uchimono for under $230
