EOS is on sale for the last couple of days. EOS is sold in multiple periods, 2 million tokens each except the first period. The tokens are distributed proportinal to the contributions for that period. Due to the nature of this distribution, a new price is set for each period.
You can follow the contribution for the current period in realtime. http://eosscan.io is a nice page to see contributions across all periods. The more money is contributed the higher the EOS token price.
In the meantime, the distributed tokens from previous days are available for trade. http://coinmarketcap.com/assets/eos/#markets
Especially irrational behavior happened during the period #2. The price of a token for period #2 ended up being 0.022 ETH. During the same window, the market price for EOS was around 0.01 ETH. Since the price of EOS only increases by the contribution for that window, there were some people who were giving money for period #2 while they can purchase EOS for cheaper (almost half price) at the market. This makes me think, there is a significant number of people investing in cryptocurrencies that are not acting rationally.