I would love to own a long arm but I just can't afford one! Long arms purchased new can range from $10,000 to $25,000 (like the Gammill Statler Stitcher). The best way to get an exact quote is to visit a dealer, and if you go to the website of a brand you're interested in you should be able to search for a dealer near you.
Another option would be a midarm (Tin Lizzie, or Handiquilter would be two suggestions that come to mind) which I believe are more in the range of $4,000 to $10,000 new. The difference is mainly in the throat space, it's a few inches smaller than a long arm but still gives you more stitching space than you would get on your domestic machine. These are something you can also find used, just like long arms, for less.