Mt Ruapehu are offering a sale on season passes before they go up in price in two weeks. I can't find the full price for this year, but last year it was $949 so likely to be around the same - I'll update if I find it.
Season passes cover both sides (Whakapapa and Tūroa), and there are options for weekday only and insurance/change-of-mind. Season passes also give discounts at the shops/cafes, and 50% off buddy passes (day passes for your mates you drag along).
Side note: For those interested in the current RAL situation, they have guaranteed that season passes will remain valid for the entire season even if a sale happens. There is a good chance that Whakapapa and Tūroa will become separate businesses with MUCH higher season pass prices (e.g. the current preferred Tūroa bidder wants to charge $1299 for a season pass that can only be used on their field).
These shall remain valid for the season regardless on how the RAL ownership/restructure/liquidation unfolds