Which sub operation is more expensive in the AES encryption process? In the AES encryption process, there are various sub-operations, like SubByte, MixColumns, ARK etc. My question is which of these operations is more expensive?  In a video lecture by Dan Boneh, it is mentioned that the lookup table implementation of AES is faster than the implementation where the MixColumns function is performed using finite field multiplication.
I do not find any information on how much faster it is? Also, is there any relation between the individual sub-operations in terms of individual CPU time?
The table lookup implementations usually combine the SubBytes and ShiftRows steps with the MixColumns step.
Different implementations/hardware/etc make general statements impossible, but this paper gives some  benchmarks and information on a table-lookup implementation.
It won't necessarily be quicker across all systems.  As per this paper:

It must be noted, anyway, that using a large amount
of memory for the look-up tables is too expensive for small systems, like for
instance smart cards, and is considered unsafe, as monitoring the accesses to the
look-up tables may in some cases allow to infer the key.

As an aside, another (better) way to speed up AES is to have the instructions built into the hardware