We were unable to swing the cost for business class on Qantas, LA-AU and NZ, any chance they will sell you an upgraded seat for less than it would have originally been?

Not likely.

You might check out premier economy on Air New Zealand.

I have to agree, there are no discounts if you purchase an class upgrade at the check-in counter. In fact if you wait until check-in time there's likely to be no seats available as they are usually given to elite Frequent Flyers.

Small chance if Y-class is overbooked...

It wouldn't hurt to dress nicely and ask nicely for a free upgrade, or just an upgrade, when you check in. But be sure to check the seat availability before you get to the airport, so you know if they are available.

Don't get your hopes up, and no need to dress nicely. QF does not sell or give out upgrades at the airport, unless you are willing to pay the fare difference. PERIOD.

They occasionally will upgrade their own elites or as a last resort OneWorld partners elites, but that ONLY happens if the economy cabin is oversold.

Other than that, I can bet the house that upgrades won't happen.

Have a great trip!