NZ is not cheap indeed and Auckland is insanely expensive (managed to buy despite the crazy housing market), but nice beaches and awesome for sailing !
Some of the central beaches are sometimes crowded, but many beaches are just empty. Went for a swim today and water was fresh (16 degrees) but refreshing !
I had thought, given how many people live around them and use them, that the beaches would be crowded, or ruined with litter, but nothing of the sort.
And the water is so much warmer than our South Island beaches.