Fireworks weren't the only thing blowing up on the Fourth of July this year. In Japan the Sumitomo epoxy plant, which made most of the epoxy used in constructing DRAM chips, blew up. Along with parts of the factory, RAM prices immediately skyrocketed. The explosion wasn't the only factor in recent price increases, since supplies have been barely meeting demand in the PC industry, which has squeezed the smaller Macintosh market.
Although the price of SIMMs was of course affected, a less obvious effect may show up in the price of configured computers. It's unclear if Apple will raise prices to compensate, or if Apple is even all that affected, given that the company was well-insulated from price shifts in the last price scare.
There's nothing to do about the problem except wait it out, although I've heard the opinion that the price jumps happening at the moment are temporary and that prices will drop again in a few weeks or a month, though not to previous levels.