If you're wondering why the ETH price has dipped significantly in the last two days, Coinbase has begun issuing reimbursements to users who suffered from the flash crash on June 21st, 2017.
For those unfamiliar with the crash, it occurred when a multimillion dollar sell order placed on Coinbase's GDax exchange exhausted all of the orders with reasonable prices, and lowered the price of ETH just enough to trigger several waves of stop-loss orders, thus plummeting ETH and causing order to complete as low as an astronomical $ 0.10 USD in some cases. Originally, Coinbase and GDax claimed that they would fully honor the transactions during the crash, allowing the market to recover on its own.
To remediate the situation, Coinbase has opted to begin reimbursing users who lost ETH in the stop-order cascade. However, they are honoring all transactions who were "lucky" enough to get ETH at $0.10, throwing a gigantic wrench in the market and bringing the price of ETH back down nearly $100 per unit at the time of writing.
And in case you were trying to get into ETH while it's on sale, Coinbase and GDax have closed sales for the time being.