> Charts like these can save you a lot of money. But it will depend on the usage of course.
You have to be careful though. For example, the Radeon RX 570 is right next to the GeForce GTX 1650 SUPER at the top of the chart, but the GeForce costs almost 40% more. If the GPU isn't your bottleneck you may be better off with the less expensive one and save money to buy a faster CPU or more memory. Whereas if it is, you may be better off spending more for a faster GPU than either of those.
What these charts are great for is to look at the top fifteen or so as the set of candidates, which will all have good performance/$, and then if you prioritize better performance look at the fastest ones and if not then look at the least expensive ones.
But even then you have to be careful. For example, on the CPU chart the Core i3-9100F is one of the best values. The Ryzen 3 3200G is only slightly faster for $17 more (i.e. almost 25% more). But the 3200G has an iGPU, which is worth a lot more than $17 if it means you don't have to buy a discrete GPU.
this is why I favor looking at the XY scatter charts rather than a made up heuristic like G3D/$. for instance those 2 gpus in you post will almost lie on a straight line through 0 without anything else on lower slope side. but we dont actually have to get the absolute lowest perf/$ & looking at the scatter chart we can bring in those other factors into play too.
In addition the most cost efficient alternative may not be good enough for your particular use-case and expectations, and then it wasn't a saving at all.
The power consumption is only significantly different under load. If you're in the corner case where Polaris Radeon is just fast enough even though you're constantly pushing its limits then this matters, but generally if you're running it at full load often enough for power consumption to be meaningful then you should be looking at the faster GPUs to begin with.
You have to be careful though. For example, the Radeon RX 570 is right next to the GeForce GTX 1650 SUPER at the top of the chart, but the GeForce costs almost 40% more. If the GPU isn't your bottleneck you may be better off with the less expensive one and save money to buy a faster CPU or more memory. Whereas if it is, you may be better off spending more for a faster GPU than either of those.
What these charts are great for is to look at the top fifteen or so as the set of candidates, which will all have good performance/$, and then if you prioritize better performance look at the fastest ones and if not then look at the least expensive ones.
But even then you have to be careful. For example, on the CPU chart the Core i3-9100F is one of the best values. The Ryzen 3 3200G is only slightly faster for $17 more (i.e. almost 25% more). But the 3200G has an iGPU, which is worth a lot more than $17 if it means you don't have to buy a discrete GPU.