alicatte, tokyo is right that full-time research active lecturers do not earn separate money for teaching - it is part of their job; and on the whole, lecturers cannot - are not allowed - to take additional work outside of their main job, unless it is directly relevant (eg earning a small fee for publishing).
Any additional money a salaried staff member earns is tightly controlled by the university such that any consultancy for example would usually be heavily top-sliced.
And on the issue of what it is that 'costs' at university, it is the expertise that is being paid for, and most would agree, I think, that this is a valuable part of university education. Those of us who work there are paid to MAKE knowledge, not just teach it. And we are paid to be scholars - to keep up with others' expertise also. This is what links research and teaching and is what is so valuable and vital to our economy and our education of the next generation of critical thinkers.
A high-rated department of professors is VERY expensive: 5 of them will cost in the order of 500k a year, plus all the more junior staff, I dunno, another 10 costing another 750k a year. If that department takes 50 students at 3k a year, you can see the costs come nowhere near. But those salaries are currently supplemented by the state, and research funding tied to specific projects. This is the problem we have: universities DO cost more than people realise.
Objectors will say - what, all that money for 10 hours a week? But the university is not like a school, or an FE college. Staff don't just teach, they design the curriculum, write the books on the curriculum, supervise and train the next generation of university teachers, produce innovations in knowledge, keep up with the forefront of their field. As well as all the other things that do happen in other teaching institutions (admin, marking, pastoral work, management etc).
It is a brilliant, soft-handed, privileged and lucky existence and no-one in the job should complain about it. But at times like this, our value is seriously questioned and it is hard not to be defensive about our value.
I would urge potential students and parents not to dismiss that value by assuming value for money has to be gained on a supermarket model. Maybe knowledge creation overall needs re-evaluating. But universities provide billions to the national economy, something that is often overlooked in the hysteria. And graduates are part of that - it isn't vocational training, it is training in thinking - a relatively small thing that makes a massive difference. Huge added value, in fact.
Having said all this - a defence, I guess, of the need to invest in universities as a common good - I still despair at the economic solution proposed. Wiping out a generation's aspirations in a stroke shows contempt for those only just gaining access to universities.
I prefer a general taxation policy myself, for all the reasons above.