Mwave currently has a sale on Arctic fans (https://www.mwave.com.au/searchresult?w=arctic) and seems their F12 PWM PST fans (White) are currently on special at only $39 for a 5 pack. This works out to be $7.80 per fan. Doing a search online shows prices ranging from $82.99 (5 pack @ Amazon) to $15 (Black version each @ PCCG) so the price seems good.
Only downside is the delivery fee, but currently delivery to Sydney, Melbourne, Brisbane, Canberra metro areas is free if you order over $100.
For anyone interested in the differences between the P and F versions, the P is pressure optimised, while the F is airflow optimised.
I first thought the PST (Power Sharing Technology) when I read about it a bit weird, but after using it I think it's a very good idea - use a single 4 pin on your motherboard and all the fans connected to it share the same speed and you don't have to set speeds per header for each fan you connect.