Currently priced at £9.48 for a 4 pack, there is also a £2 voucher
available, which take you down to £7.48, and if you take the subscribe and save option (cancel later after delivery) then price goes down £7.01. Further 10% off if you have 4 other items on subscribe and save.
At last than £2 a piece, you will not find a cheaper deal for the 3D brush. Precision head can often be had for less than £2, but for 3D its once in a blue moon.