Apple (AAPL) closed at 228.36 Tuesday, up 3.61 points (1.61%) for the day to hit another record high — its seventh since March 5.

    While the whole market was up Tuesday — and tech stocks in particular — Apple has been enjoying a particular strong run. Its shares have climbed nearly 14% in the past month and more than 36 points since Feb. 4, when Wall Street went cold on the stock in the wake of the iPad's unveiling.

    Since then:

    • iPad pre-orders started off with a bang

    • NPD reported Mac sales up 39% year over year

    • Apple slapped a key iPhone competitor with a big patent suit

    • And Steve Jobs came out of his shell, appearing at public events and firing off e-mail one liners

    But underlying all these factors is the strength of Apple's business model — creating a select portfolio of high-value, tightly integrated products and selling them at premium prices.

    The payoff is visible in the bar chart below, prepared by Deutsche Bank and chosen by Silicon Alley Insider as its chart of the day. The bars show the revenue and operating profits of the world's 10 largest 10 PC makers in 2009. Note that while Apple had only 7% of the PC industry's revenue last year, it pulled in 35% of its operating profit.