depends entirely on what you will use it for and how you'll use it. do you need ultraportability or will it mainly sit on your desk? do you need a big screen? will applications will you be using, which will determine CPU, HDD, GPU, and RAM. You can get a tremendous amount of power for decent prices, and if you shop around and look for coupons, deals, and discounts, you can stretch your dollar even more.
You'll be hard pressed to find a totally useless laptop, but you can definitely spend more than you need for too much power and features.