Hello cyrilp,
Note that for simultaneous work on different machines you require separate Metashape license for each machine.
As for the hardware configuration, what are the typical projects you are planning to process (survey type, image resolution, processing steps to complete and parameters to be used)? For GPUs you can use previous generations, like GeForce GTX 1080 Ti, RTX 2080 Ti, for example. Not sure, if it is common in most of countries, but in our local shops the price of new GPUs are extremely high (for a couple of month the price jump is about 1.5-2 times for RTX 30 series), so probably getting GTX 10 or RTX 20 series cards would save you some money. You can opt for dual-GPU setup with two 2070 or even two 2060 cards to get performance comparable to single 2080 Ti.
Also if you are not working with extremely large datasets, then 64 GB RAM will be sufficient.