A couple more notes: There's the old claim that a knight's sword cost more than a peasant's yearly earnings. If you look at modern day peasants who live on $1-$2/day, and figure that a decent modern sword is around $500-600, you'll see that things really haven't changed much.
While I can't speak to 1800 swords, I've seen some very high quality 1900 era Chinese jian, and I would guess that there was the possibility of high quality weapons in earlier eras.
Third note. Back when I was a kid, I was into RPGs (the games, not the weapons
), and I learned a little trick. That trick is that gold tends to keep its value over time. If something cost a penny then and a dollar now, you can bet that gold's value has also increased 100-fold. This is not strictly true now (thanks to rampant speculation) but it's a good rough-and-ready estimate if you're in a hurry.
With the sword example above, price your item in gold (per gram, ounce, or whatever), find out what gold was valued at in your era of choice, and that will approximately be the value of your item back then. If you don't want to deal with gold, livestock also works fairly well, although I don't know what a pig or cow is selling for right now.
For example, a sword right now is selling at between about 0.3 and 1.0 troy ounces of gold, approximately ($250-$1000) (with better ones going for 2-3 troy ounces). What's that in 1800 Chinese money?
Best,
F