There is. High price encourages people to buy/start their miners. Many of them didn't expect to receive their orders late when the difficulty was already high and they didn't take into consideration that the difficulty increase due to increased demand would be so huge. Even when unprofitable or barely profitable people will mine for some time waiting for a change in price (increase) or difficulty (decrease) that would make their mining more profitable or waiting until someone buys their miner(s).
Difficulty adjusts itself to the price with a considerable time lag, one can see how it occurred in 2011.