They got a little over 19,000 last year for Day 1 last year in Perth, granted it was 39 degrees but it's a pretty average crowd. I'm not expecting a big crowd here in Perth this year given NZ aren't exactly a big draw card, maybe the D/N Test can draw the people through the gate but I'm not gonna hold my breath.
Last year's crowds for Perth Stadium's debut test were very poor, considering India is generally the 2nd highest drawing nation in Australia after England (with the Ashes):
Day 1: 20,746
Day 2: 19,042
Day 3: 19,757
Day 4: 10,887
Day 5: 10,672
Btw, Adelaide Oval today got 10,052, making it a total of 91,879 across the 4 days, nearly double what the Gabba got (45,991).
At least that's the Pakistan series out of the way. Bring on New Zealand!