[Brightcolours]

But regardless, overall, APS-C is much cheaper than FF.

Lets examine that then?

One of the most prolific Fuji X-mount lenses is the 56mm f1.2 R. US price: $999.
FF equivalents:
Tamron SP 85mm f1.8 VC USD. US price: $749.
Canon EF 85mm f1.8 USM. US price: $420.
Nikkor AF-S 85mm f1.8 G. US price: $477.
Sony FE 85mm f1.8. US price: $598.

Hmmm...

Ok, I'll try again. 

One of the most prolific Canon EF-M lenses is the EF-M 22mm f2 STM. US price: $249.
FF equivalent:
Canon EF 40mm f2.8 STM. US price: $199.

Seems that FF equivalents are not more expensive, rather it looks like only slower APS-C lenses are cheaper than faster FF lenses.