Most of the steamers sold in retail stores are cheap copies of one of these:
http://www.myvaporclean.com/SF233_1_.htm
Yes, these cost a lot more, but they are very useful tools that will last for years. I lucked out in the early days of Craigslist and bought a Vaporjet for around $200 from a guy who used to own a restaurant. The continuous fill makes the machine much more convenient when doing large jobs. I don't care how much you change your mop water, your hard floors will never be as clean as when it's been steamed.