The big difference is number of cores you have to work with, and to a lesser extent the amount of RAM. For say 800€ you can get probably a 4 core CPU, maybe 8.

The big difference is number of cores you have to work with, and to a lesser extent the amount of RAM. For say 800€ you can get probably a 4 core CPU, maybe 8. I guess 8GB RAM? Or you can get 10 raspberry pi 4s for a total of 40 cores and 40GB RAM. What makes more sense for you will depend on your workload and scaling requirements.