Yes, in a developed and efficient market, price manipulation would not be possible. If somebody does try to manipulate markets, he would get caught and be prosecuted. Unfortunately, that doesn't happen in crypto-markets.
It is always easy to manipulate the price by changing the money supply. We just witnessed that FED printed 5x USD to make sure the housing price does not crash as they should, this is the largest scale market manipulation in human history
In principle, no one could change the money supply on crypto-markets, so theoretically it should be close to ideal free market. But currently the economy scale is still too small, any hedge fund would be able to manipulate the exchange rate. However, the ability to manipulate it down is limited, due to limited sell pressure they can generate
