Hi
1. Dependence on hardware
Tool for comparison
https://www.chaosgroup.com/vray/benchmark
here is some characteristics
http://benchmark.chaosgroup.com/cpu - there you can switch CPU and GPU
comparative table by time
http://benchmark.chaosgroup.com/gpu/details?hw=Intel ®% 20Xeon ®% 20CPU% 20E5-2630% 20v4% 20% 40% 202.20GHz% 20x20% 2C% 20Quadro% 20M2000% 204096MB & id = 2383
2. Dependence on the price of the farm on which the equipment is installed.
For example, from this list, the price difference for the CPU https://rentrender.com/all-render-farms-list/
price for GPU https://rentrender.com/gpu-render-farms-list/
The rest depends on the budget and terms (deadline) of the project
