The great majority of swords sold as antique Chinese on eBay are fake.  They are exemplified by the many listings with a $.99 price and $100 shipping from China.  Many of these will have folded blades with what loks like a nice Damascus pattern, but they are still junk.  The steel is too soft, the balence is wrong, and the blade is too heavy.  These are quite recognizable after looking at a few listings.  The pattern is indeed formed by folding the steel, but the techniques are crude, and there is no attempt made to temper the blade.  Do not buy these even if they look pretty, unless you are planning on hanging the sword on the wall only. 

The next catagory is swords with some age that are not worth the asking price.  The most commenly seen example is the double edged short sword (duan jian) with a tortoiseshell scabbard.  These are indeed antiques, but were made origenally for the tourist trade 100 years ago and are consequently of low quality.  They are often sold with a good story for many times what they are worth.  These are often sold by unscrupulous dealers outside of China, but within China counterfits of these counterfit swords are starting to appear.  Chinese sellers will also mix genuine antique blades with reproduction fittings.  Often these are also not worth the price asked.  However, sometimes decent deals can be found.  One has to have a good eye to spot what has been replaced and what is original.  I look for original hilt fittings on a decent blade, and expect the scabard to be a reproduction.  Reproduction hilt fittings on a beat up blade are not worth much.

The last catagory is the genuine antiques of good quality that are occasionaly sold.  Reputable dealers command high prices and the swords are worth it.  Disreputable dealers can also ask for high prices, so be careful.  The best deals are the ones that are the most risky.  These are the Chinese sellers who sell fakes, mixed fake and real, and real swords without any good way to tell them appart.  Do not attempt to buy swords like this unless you can already tell fake from antique from a picture.  It is very easy to get fooled, and the fakes are getting better every day.

Josh