The graph is pretty easy to understand. This videocard gets this framerate for this price, that one's a little better, these two together get this much, so on and so forth.

While the chart is good in the way that it is simple and tells which card is worth how much, the framerate is really a guestimation. How can four 9800 GX2's, in quad SLI, not run Crysis at 40FPS on high?! I run Crysis on high at 1920x1200 with an 8800GTX, and it gets 25FPS.

But if you take the chart with a grain of salt in terms of the framerate, which obviously will vary based on other factors than your videocard, it's a very useful bit of information.

Tech Report