You have to put in the graph all the info needed by the reader. If price/power/performance are of use then you have to put the three.
3D graph are quiet hard to read, especially when you deal with discreet points rather than with continuous area (like altitude on a 3D geographical map that you can draw with different colours)
On a 2D graph, if you keep the 3 parameters you have to weight them. The exemple 'score/($ x W)' suggested, gives the same importance to price and power. Some people favour price, other power, so that's not a solution.
Narrasuj suggested a dynamic graph where the reader can weight himself between the 3 parameters. That's significantly harder to implement on the web than a simple jpeg graph.
A solution would be to put only 2 parameters in the graph, and keep the third out of it.
Aris wrote:prices may be difficult as they always change. so rather than real world prices you could just put in the initial MSRP from either ati or nvidia for that card.
Good point, I remember seing a graph of processors rated according to their price and performance. The graph was one year old and was sadly totally useless as prices of Athlon, Duron, Pentium and Celeron got different price cuts during that time.
So puting the prices in the graph would need a regular update of the graph or it will become inaccurate after 6 months or so.
Performance and power consumption being the only 2 numbers staying constant over the life of the graphic card, they are probably the easier one to put in the graph. You can then insert under the graph the lower price of each card hotlinked from a price grabbing website.
But I keep writing and realize I have absolutely no will to do it myself, has anyone voluntereed yet or have we to choose a volunteer ?