Fractal Design Venturi Hf-12 120mm Case Fan $19 (Normally $29) @ extreme pc

Cheapest ever. Normally $29.

Bearings are fluid dynamic bearings and cfm of 82rpm @1400rpm 19-25db. You'd be hard pressed to find a non sleeve or ball bearing fan at this price that pushes this much airflow at low rpm and noise.

This is the airflow version (case) and not for static pressure (I.e. Cpus and radiators)

Reviews are very favourable. Learnt all about case cooling recently after upgrading to a 7700k and running temps were up to 90 degrees under load. Now with 4 additional case fans it now only reaches 67 degrees under load