Switch: mikrotik CRS504-4XQ-IN ($799.99) Cabling: QSFP28 to 4 x 25G SFP28 DAC ($63.00 per cable) NICs: Intel XXV710 25GB ($349.0)
I don’t know how many machines you have so for two machine it’s cost you $1562.97 and maxing out the switch would cost you $6651.83 but do you really have sixteen machines that need or can even physically saturate a 25GB line?
I think it’s more reasonable to get something similar to ubiquiti’s USW-Pro-Aggregation and have three machines capable of the full speed and 28 machines capable of half rate speeds (at a much lower cost per machine)