To write a few lines of code it cost more than building an entire application, why that ?

In my opinion, there are two main factors: (1) Lack of professionals with expertise in Solidity; (2) The amount of capital raised through ICOs. There are a couple of great projects that demand lots of Solidity devs raising a bunch of ETH. On the other hand, there are fewer Solidity devs than spots available. I personally believe that the projects must also contribute with the ecosystems they are inserted in by creating meetups / events, creating the local communities, and providing knowledge for free to anyone interested. Swapy Network's team (http://www.altcoinstalks.com/index.php?topic=2195.0) is actively engaging people locally through (https://www.meetup.com/Ethereum-BH/). Do anyone see other factors?

Ethereum has a huge potential. There are lots of altcoins being built on top of it. Since they needsto pay gas on every transaction, the demand for ETH will increase. As soon as some of the projects become popular, ETH price will go up.