First of it's a seat stem not steam, steam is liquid vapor.

The Nitto is expensive because it's the best aluminum stem with more adjustments, as well as the most polished looking stem on the market, and will last a lifetime. If you don't need a stem to last a long time or look great then just get the el cheapo stem.

The upgrade may be lighter, but I don't know what your comparing it to, no stem will absorb shock unless it's got a built in suspension system; you'll have to get a seat that can do that to some degree.