Is it fine to feed my cat Wet Food only Once a Week??

i feed my cat dry food but i don't worry because its healthy. thats what the vet recommended to me. i don't know the name because its french word/letters/ its kinda expensive. anyways,,, i can only feed my cat wt food once a week because its too expensive of 1 can only... it is okey for that even the cat dry food is healthy???