Well we've got to be a bit careful when we use the term 'cost' here. Cost inputs to produce law/economics/philosophy are sweet F all compared to some of the inputs required to produce science/medicine/etc. And then we've got the university internal-cross-subsidisation structure between degrees, as well as the full-fee paying structures for immigrants/externals.

The 'price' of the degree is not based on cost/demand, but essentially by government decree of which fee structure it sits in. I got my economics and arts degrees when they were in the lowest and medium bands (IIRC), and now they're in the highest bands, and its not because of the cost of supply...its because government policy is trying to use 'regulated price' as an attempt to bend applicants to particular areas it desires.

Add on our HECS system (whereby graduates pay back their student loans via our tax system upon employment) and suddenly the simple idea of tax payer covering the cost of these degrees becomes incredibly murky...