It's usually on sale for $30-40 but now it's down to $5usd/$7.50nzd. There's an additional $10usd discount on games over $15usd so this game is double discounted, provided you haven't already used the $10 discount on another game, otherwise there's other games you could use it on such as Borderlands 3 which is $42nzd, but $7.50 for WWZ is a stupidly good deal.
If you used the discount on another game, you should have gotten another discount coupon. That's how it's supposed to work at least.