I am a nurse in this dialysis center for a year and a half now.
we occasionnaly recieve visitors from other country (new zealand, hawai, usa, australia...)but this is quite rare.
most of our visitors are from france, so the dialysis are free (french health system still works...)
the cost for one dialysis is, I supose, around 500 euros, as a dialysis is around 300 in france.
I cannot be positive about that though....

my advice might be more interesting about the quality medical cares and respect of hygiene, which ARE very acceptable.
doctors and nurses are good willed and the proximity of a good range of medical services makes the dialysis very safe.

you might know that visitors often get their dialysis by night (from 8pm to 3 am)

also remember tahiti is not the most marvelous place in french polynesia, so get ready to go and visit several islands with no dialysis centre.to do so , you might have to stay 3 to 4 days without dialysis (if you can) to fully enjoy these wonderfull polynesian treasures.