is my performance slow?
I issued this command:

hashcat -m 2500 -a 0 -r ../../dict/rules/best64.rule test.hccapx ../../dict/oCustom-WPA.txt  -o cracked -w 3 -O

Hashcat said this:

Host memory required for this attack: 1166 MB

and this

Speed.#1.........:  1143.0 kH/s (72.16ms) @ Accel:32 Loops:128 Thr:1024 Vec:1

I have 32 gig ram. Why does it only use 1166MB? The dictionary file is 2.2 gig.
Other examples show people getting megahashes per second.
I have CUDA installed and am running a 3080 but only get 1143 kilohashes/s.
Your guessing rate 1143 kH/s is extremely good for WPA.

Even the most expensive cards one can buy do not reach more 10000 kH/s which is required for hashcat to switch to MH/s. You probably confuse the hash mode or not single GPU.