Focal length and FStop

I have been reading about Focal length and Fast lenses when I came across this lens which has 85mm focal length and F1.4 as FStop.

Generally lenses with 1.4mm Fstop have focal length below 35mm but here its 85mm!!
As we calculate FStop as FocalLength/diameter this implies that this lens must be having huge diameter to achieve 1.4 Fstop.

Looking at cost this lens is very expensive, so must be a premium lens.

Can someone please explain how having a large diameter makes it a premium lens.