On a simple level the more expensive cards have more transistors, more VRAM, and hence are faster and support running bigger ML models if your models have high

On a simple level the more expensive cards have more transistors, more VRAM, and hence are faster and support running bigger ML models if your models have high VRAM requirements. The newer generations also have a spate of new gaming, video, and ML technologies that make some aspects of all those things faster. TDLR: More expensive = better.