It is cost rather than privacy concerns that will save us from Labour's megalomaniac surveillance schemes – a point underlined this morning when David Cameron was interviewed on the Today programme. With the vast choice of public expenditure open to him, he would single out only the identity card scheme and the children's database ContactPoint as definite targets for immediate cuts.

There are many more savings to be made. Earlier this year, I and a couple of researchers started to calculate the costs of the database state and came up with a total of about £35bn from published figures. The Rowntree Trust followed with a report that claimed that £16bn was spent each year on IT schemes and that spending plans over the next five years amounted to £100bn.

So we are talking very big figures indeed, although no one really knows how much the surveillance state will cost. When you confront civil servants like Sir David Varney who is in charge of the transformational government project, which will make all information about individuals available to all departments and agencies, they say that the savings will pay for the scheme.

But recent investigations by the Times and Computer Weekly showed that the overrun on large-scale IT projects totals £18.6bn. For instance, the cost of the NHS Spine – a controversial plan to computerise all patients' records – has risen from £2.3bn in three years to £12.7bn, and the system still is not working.

Here are some figures:

ContactPoint

The projected cost of the database, which will contain the personal details of every child of school age in the UK, is £224m with operating costs of £41m per annum over 10 years. The total cost of ContactPoint is £634m.

ID Cards and national identity register

A report in June 2005 from the London School of Economics predicted that the ID card scheme would cost in total between £10.6bn and £19.2bn over 10 years. The original Home Office estimate was £3.1bn. The official figure was revised up and down to £5.4bn and £4.5bn. The difficulty with the ID card scheme is working what the Home Office has passed on to other ministries and what costs it is hiding. Most estimates outside the government believe the final bill to be somewhere between £10bn and £11bn.

e-Borders

The e-Borders scheme will monitor everyone crossing UK borders. Those leaving the country will be expected to supply up to 53 pieces of information to the government. The estimated cost over the next decade is £1.2bn. Costs to the UK travel industry for the same period, which are expected to be passed onto the travelling public, are £360m. Therefore costs to the taxpayer and indirectly to the public equal about £1.5bn. Again this is unlikely to be the final story, especially when you consider that £650m alone was earmarked for the Raytheon Systems over the next 10 years. As yet there is no publicised estimate for the spy centre at Wythenshawe, which will track all our movements. Known costs are about £1.5bn.

Interception modernisation programme

Proposed in the communications data bill, the IMP will store data from every text, phone call, email and internet connection. The costs of the data silo are estimated at £12bn, although the Home Office has suggested it might be run in the private sector. Experience suggests this is unlikely to cut costs and that the security of the system would be compromised. Estimated cost: £12bn.

Automatic number recognition camera network

This system tracks, records and stores the details of all journeys undertaken on major roads and through city centres. The information is stored for five years. In 2007 this was said to have costs £32.5bn in funding with a further £10m since then; a total of £2m per annum is spent. The final bill over five years is £52m.

NHS spine

This is a computerised system linking health records. Estimated cost: £12.2bn.

Some important points: first, a lot of this money is being spent with foreign systems companies; second, the government has never produced a global figure for the surveillance state; third, there are no estimates of the vast amounts of money being wasted locally, for instance on CCTV schemes, which are held by police officers and the House of Lords to have little effect on crime reduction.

If people with knowledge of the economics of surveillance are reading this, they may like to help to refine the bill.