Mountain bikes are all very expensive. The frame is the heart of a mountain bike. Once you replace the frame it's a different bike but if the bike comes with mediocre parts on it you can replace them anytime.

If you want a bike that is too fancy and radical looking and yet cheap you will get one that is not good enough. The traditional diamond frame is the best. The only exceptions in the price range are bikes made by Haro or GT. These bikes only have small variations on the diamond frame.

You can howerver, get a great used mountain bike at an online auction site. There are thousands of people that thought mountain biking was easy and others that are looking to upgrade to the next step up.

The expensive bikes come with suspension specifically designed to make them easier to ride uphill. Most mountain bikes these days have disc brakes. These offer improved stopping power over rim brakes under adverse conditions as they are located at the center of the wheel and therefore remain drier and cleaner than wheel rims, which are more readily soiled or damaged. Disc brakes offer the capacity for sustained heavy braking with fewer problems of brake fade than are encountered with rim brakes. It allows greater safety margins with less rider fatigue, greater modulation and therefore much more control. Mechanical disc brakes are relatively less expensive than the hydraulic disc brakes. Hydraulic disc brakes work by moving brake fluid through a hose or line to squeeze the pads together. These brakes require much more technical maintenance. They also enjoy much longer service intervals than the mechanical brakes.

The cost also depends on the wheel and tire. There are a wide variety of patterns available like slick street tires, street tires with a center ridge and outer tread, fully knobby, front-specific, rear-specific, and snow studded. Some of these are made specifically for certain weather conditions. Others all for all purposes. The more expensive tires tend to be lighter than the rest and have less rolling resistance.

So if you are going to try some rough stuff then you need all of this and much more. Suspension is a must. Gears will probably be Shimano, brakes must be V-brakes. A better and costly mountain bike will have a sportier handling. It will be lighter and so it will be easier to struggle up the hills. The components will again be Shimano and the quality will depend on how much money you can afford to spend. V-brakes and Rapid-fire gear shifters, along with Shimano chain set, bottom bracket and headset. Handle bars, stem and seat pin should be there as well and along with a comfortable saddle you'll be set to take to the hills.

Trek, Giant, Specialized and Cannondale, these companies make the nicest frames with the best mountain bike parts available. Gears will be either Shimano or SRAM, brakes could be V-brakes or cable disc brakes. Both are very good and light. Then you have to choose which suspension forks to put on your bike. You might not get a choice, however as it depends on which bike you buy. The main ones are Suntour, Marzocchi, Manitou, Fox, RockShox and RST, buy any of these and you wont go far wrong.