It is clear from this excellent novel that the pair pay the highest possible price, though as we progress it also becomes clear that it is Kino who drags the pair on into the ever-increasing path of destruction and death that the pearl leads him to embark on. Note the way in which the pearl becomes so important to Kino that he says it is as important to him as his soul:
"This pearl has become my soul," said Kino. "If I give it up I shall lose my soul."
Ironically, of course, this is completely true, as when he does give up the pearl, he has already lost his soul, metaphorically speaking, in the form of his son. This is the priceless price that the pair pay for the pearl, and note how the pair are described on their return to their village and the sea:
Her face was hard and lined and leathery with fatigue and with the tightness with which she fought fatigue. And her wide eyes stared inward on herself. She was as remote and as removed as Heaven. Kino's lips were thin and his jaws tight, and the people say that he carried fear with him, that he was as dangerous as a rising storm. The people say that the two seemed to be removed from human experience; that they had gone through pain and had come out on the other side; that there was almost a magical protection about them.
They have, losing their son, metaphorically lost their souls, which is why Juana and Kino appear to be "removed from human experience."
His baby died.
the price they paid for the pearl was that they lost all their belonings ie. canoe, hut. they also lost their son because of the pearl .