You do not multiply all of these together e.g.

Xeon GOLD 5220 2.2G x 2Sockets 18Cores 36Threads = 2(processors) x 36(threads) = 72 Logical Processors (vCPU)

purchasing is based an units of 32 cores per processor so your proposed ESXi 8 processors would both need 2 licences 

Xeon Gold 6430 2.10 x 2Sockets 32Cores 64Threads = 2 VMware licences

Xeon Gold 5415+ 2.90 x 2Sockets 8Cores 16Threads = 2 VMware Licences