If difficulty was going up at this rate with only GPU miners, in the interest of their own profitability I think they'd all be asking for higher prices. ASIC miners are in their own golden age now, making money hand over fist, and are willing to take this price.

Meanwhile, volume is affected by the moderate drop in media attention post-crash, and the most "user-friendly" exchange becoming significantly less so, with a lack of comparable alternatives stepping up to fill the gap. The higher barrier to entry and lower volume reduces speculation that could jump the price up more regardless of miner profits.