Dude, there is NO CORRELATION between price and difficulty period lol. Price got pumped last year due to hype and good news from media. That seems to have died down for now.
There is no direct and instant correlation but the price will always affect difficulty.
Let's say the price goes to 10$ (for the sake of the argument), who is going to mine? Those that don't give a damn about profits and those that get free energy. Expect the difficulty to go back by a few (more) digits.
The same if the price spikes up to 100k. With so much money as reward for each block people will plug back block erupters.