First off, I am sure it was 120 GRAMS, not kg. Also, that amount is not "needed" for survival. However, there is support in peer-reviewed medical journals that even higher levels of protein will optimize muscle gains, which is something that would be relevant to certain populations, such as bodybuilders.
That being said, protein powder is a great thing to include. Whey concentrate will always be cheaper than isolate. Honestly, unless you are lactose intolerant, there is no reason to pay extra for the isolate.
I personally use protein powders to supplement my dietary protein intake on a daily basis. It is actually very inexpensive way to get protein when you consider the per gram cost. I buy on a sale and purchase 80-100 pounds at a time,. The expiration date is usually 3 years from date of manufacture, but if stored in a cool dark place, it will last a few years after that. I am not sure how long the shelf-life would be if you opened up a tub and vacuum sealed it, but fat content will shorten shelf-life.
As for the comment above about protein without fat and carbs, I don't think that anyone actually is only stockpiling protein powder with no oats or pasta or any other carb source. The great thing about protein powder is that you can cook with it or just mix with water and drink it like a shake.
yes grams, obviously
There are reasons for isolate over concentrate and there are reasons for concentrate over isolate.
isolate has a higher protein ratio, meaing you get more protein in an equal amount of powder
example in a 10lb container you are getting perhaps 1 pound or more protein with isolate than concentrate. (ratios depend on the brand and product)
So if you pay 10% more for isolate for protein content the price is equivocal.
Isolate absorbs faster which makes it a good post workout drink
concentrate is often slow release and takes longer to absorb which makes it better for a recovery protein.
Protein intake will depend on muscle damage, body builders tear a lot more muscle than other forms individuals, atheletes who are actually training and competing will need a higher intake than a casual gym goer. Sedentary people who don't work out to build muslce require lower protein intakes to require their level of fitness.
Serious body builders with lots of muscle to repair can benefit with levels up to around 1.6 if timed property for release, as there is a maximum hourly protein absorption rate. I am moderately active so about 1.2 is enough for me to have slight gains. You can have even greater gains at higher than 1.6 but it is mostly negigible, but you need to intake fat roughly in ratio with protein to prevent rabbit dieting with results in fat loss due to high protein intake.
http://en.wikipedia.org/wiki/Rabbit_starvation
With fat intake increases calorie intake goes up, which requires higher amounts of exercise, there is a threshold involved. You also need carbs to increase for some sorts of energy not an absolute but it helps which glycemic ratio which give the body actual energy for endurance.
so basically as protien goes up fat goes up as fat goes up activity must go up, as activity goes up carbs must go up... this can be contrast between the basal metabolic rate (varies from person to person based on organ output levels) and the amount of energy expended to manage muscle gain and weight in fat holding ratio.
then you have the fibre element and water element which allows waste byproduct to be removed and recovery to be enhanced.
