Right now, valuation is irrelevant because factors largely unrelated to the company are driving selling. Some of these include tax gain selling, funds selling to protect their "better than their index" performance for the year attributable to being overweight AAPL, tax loss selling for those who bought above these levels, some short selling from those understanding these factors, and margin calls on some. At the same time, demand is weak because there is uncertainty about whether people can get in lower if they wait another week or two.
I have no idea how low the stock goes, but if we haven't reached bottom yet, we are running low on time to get there IMO. When the year ends and earnings approach in January, these factors will turn the page and valuation will matter. Fund managers will buy back in to get a fresh start on beating their index in 2013. And, it doesn't hurt that analysts have used this period to lower estimates; giving fund managers even more confidence to buy. Whether this coming week, the final week of the year, or early January, I believe we will experience a very nice move up into earnings.
Right now, AAPL is valued lower than MSFT and INTC, both companies participating in a secular decline with weaker financial metrics. AAPL participates in 3 businesses, with phones and tablets being growth businesses and the iMac having low market share and great potential. AAPL deserves a better valuation by some order of magnitude over MSFT and INTC.