As the number of features goes up, so does the price.
You can spend over $800.00 on a GPSr that has a built in camera, light and all the topographic maps of North America. If you program it correctly, it will go get the geocaches for you, sign your name and replace them perfectly for the next cacher. Well, almost. The point is that the more features you want, the more the cost will rise. Other advanced features may include; Backlit screen, color screen, expandable memory (using removable cards), rechargeable battery, compass, water-resistance and the ability to send a signal to have rescuers find you. One other thing to keep in mind is that newer models are coming out every year, with more and more advanced features. Waiting and doing your research before purchasing should help you find the best GPSr for your needs and budget.