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.
Just for curiosity, what are the differences between pressure optimised and airflow optimised fans?