With a few exceptions, sweet science memorabilia is still inexpensive.
Boxing collectibles go back at least as far as baseball. You won't find quite the frenzy over a rare 19th century boxing piece that you will with a baseball item, but the sport still has a loyal following among some collectors.
It takes a true fight fan to want Larry Holmes' old robe, but a few boxers transcend the sport and cross into the mainstream of sports memorabilia.
The Wall Street Journal has a little primer on some recent sales and an overview of the market. It's news you can use (if you can get past the paper's annoying policy of calling everyone "Mr.")