of pu-erh tea will change to be better and better, so aged teas are better than new teas. The aged pu-erh teas can be sold at the higher prices, so many people buy the teas for investment.
Pu-erh teas also are a kind of healthy teas. It is said that the pu-erh teas can lower the cholesterol, reduce the blood fat, help the digest and be anticancer. So the tea becomes more and more popular.