Like Riyko said, the price of the computer depends on what is inside. However, on the issue of laptops, price is also affected by portability. The small, sexy, and not as powerful laptop could cost more than the heavy bulky more powerful one.
Usually, the lower priced laptops are laptops with older technologies in them.
What you need depends on what you are going to do with it. Laptops are generally not as powerful as their desktop counterparts because of space and heat restrictions. So, everything must be engineered around this.. causing the price to go up. So even though you see $2000 laptops, they still won't be able to play the latest and greatest games at acceptable speeds because of this.
Regardless of what you want a laptop for, I would go with a laptop that has at least a dual core CPU (core duo, core duo 2, Turion X2),has 1 gig of ram, a decent graphics card from Nvidia or ATI, and built-in wireless 802.11g.... as a minimum starting point.
Ergonomics-wise, get a laptop which has all the ports and drives in places that makes sense to you. Normally, the optical drives are swappable... meaning that you can take it out and put something else in it's place... such as an extra battery or a different optical drive (blu-ray, hd-dvd).
Also make sure that vents to exhaust the hot air from inside the laptop are *NOT AT THE BOTTOM OF THE COMPUTER*. Sometimes laptops, when you put them on the table, have a small gap on the bottom to let air flow underneath. What some engineers haven't figured out is that some people put their laptops on their bed or on their lap which eliminates this gap... If the vents are on the bottom, you are at risk of overheating your laptop.
Also, look at what is cooling your laptop... fans? How loud are they and how often do they come on? How many fans are there? I used a couple of Dell laptops and when the fans (2 of them) came on... it was like a jet engine was starting up... it was loud.
Ask if the memory is upgradeable, how much will it cost, and what is the max memory capacity allowed.
One of the biggest complaints about laptops is the keyboard. Laptop keyboards come in all shapes and sizes and they feel different when typing on them. So make sure you get a laptop that has a keyboard you are comfortable using and all the buttons are in places you expect them to be and sizes you expect to be at. There is nothing more annoying than having the backspace button the size of a regular button because it is one of the more common keys people press. It should be a wide button... like the space bar... but not as wide. You know what I mean.
Screens nowadays are becoming a concern. I've seen the newer laptops with the fancy glossy screens. They look awesome in regular office lighting. However, my coworker has one in his office and he sits with the window to his back and so when it gets sunny, the glare is extremely annoying. It's like you can see what's happening behind you without even turning around.
Anyway, I hope I've helped you with some of the experiences I've had with laptops.
BTW, if you are specifically asking for brand, the most reliable laptop I have ever used is a Sony Viao. It was damn expensive.. but after 6 years, I still have a use for it as a test web server. It is a Pentium II 266mhz, 192mb ram, 4 gb hard drive, and built-in graphics card with 2mb video memory. I think the calculators you can buy today are more powerful than it, but it's still got value