The materials used to manufacture the frame determine the strength, longevity, weight, riding experience and of course, the price.
Mostly, alloys of aluminium are used to manufacture the mountain-bike frames. The manufacturers sponsor or undertake research to incorporate innovative tubing designs and manufacturing processes in producing their bike models. The high-end costly models use lighter and sturdy aluminium alloy frames.
Carbon fiber, steel and titanium frames are also used for manufacturing mountain bikes. The steel frames are inexpensive and strong, but their weight makes them unsuitable for mountain riding despite smooth performance. On the other hand, titanium frames are stronger and lighter, but they increase the cost of mountain bikes. The carbon frames are expensive due to labor-intensive manufacturing process, but prove to be relatively cheaper option as compared to other costly materials suitable for high-end cross country or mountain bikes.