BLender has a benchmark page, and there are numbers all over the place, you can't tell whats a real benchmark.
These videos show people rendering using a 3070 etc, and you can see how long.
This video the person has benchmarks for 3070 to 3090, and also if you have 2 in a system. So 2 3090's have a benchmark of the bmw scene at 11s. For a comparison, a 1650 is 2min. But not everyone including me can afford one, so a 3060 or 3070 is still pretty good.
And this guy has 2 rtx3090 gpus in his computer. Just jealous. But he never said how much that costs.
I ran some benchmarks on some Low end computers, and it's interesting to note that changing the tile size from 256 to 32 changes the render time by quite a lot.(shorter) It's also noteworthy that the gpu seems to matter more than the cpu. THe laptop isn't as fast as the amd in terms of the cpu, and the nvidia 1050 in the faster amd system has roughly the same benchmark as the laptop with the i5 2.6ghz with the nvidia 1650. So if your trying to do blender on a low end comptuer, don't use cycles at all. Use eevee.
3 min 43 degrees in an 85 degree room.
10 min 56 degrees in an 85 degree room.
Both systems have 16gigs of ram.
amd 5600x and Nvidia 1050
bmw cpu gpu tiles 512 512 cuda no denoise 3:40s
bmw cpu gpu tiles 256 256 cuda no denoise 3:08s
bmw cpu gpu tiles 64 64 cuda 2:04s
bmw cpu gpu tiles 32 32 cuda no denoise 2:03s
bmw cpu gpu tiles 32 32 optix no denoise 2:03s
Bmw cpu tiles 256 256 cuda 6:11sec
Bmw cpu tiles 32 32 cuda 4min
Nvidia 1050 only
Bmw Gpu Nvidia 1050 2 gig vram 256 256 cuda 4min
Bmw Gpu Nvidia 1050 32 32 cuda 3:24s
I5 and Nvidia 1650
bmw cpu gpu tiles 256 256 cuda no denoise 2:30s
bmw cpu gpu tiles 32 32 cuda no denoise 2:10s
bmw cpu gpu tiles 32 32 optix no denoise 2:07s with optix
bmw cpu gpu tiles 32 32 optix with denoise 1.33 with optix set as denoising option
bmw cpu gpu tiles 32 32 cuda with denoise 2:19s
bmw cpu gpu tiles 32 32 optix with denoise 2:19s with optix
Bmw cpu tiles 256 256 cuda 11.33min
Bmw cpu tiles 32 32 cuda 9min
Nvidia 1650 only
Bmw Gpu Nvidia 1650 256 256 cuda 2:47s
Bmw Gpu Nvidia 1650 32 32 cuda 2:34s
Look at the hardware page for the complete specs.