The Metropolitan Police has now spent £37.4m on investigations into journalism, with the figure rising by nearly £4m in the last eight months.
Newly-released figures show the total cost of Operation Weeting, investigating phone-hacking, is now £21m.
Operation Elveden, the probe into payments to public officials which has come under scrutiny in recent months, has cost a total of £13m.
And Operation Tuleta, into computer-hacking, has so far cost £0.8m.
The figures exclude legal costs.
The Met Police figures show that investment in Operation Weeting has shrunk each year since it was started in January 2011.
It cost £6.4m in the 2011/12 financial year, £5.8m in 2012/13, £5.1m in 2013/14 and £3.7m in 2014/15. The previously-released figures, published by Press Gazette and correct as of September 2014, showed the operation had cost £19.2m, meaning £1.8m has been spent in the last eight months.
Elveden, meanwhile, cost £1.6m in 2011/12, £4.1m in 2012/13, £3.9m in 2013/14 and £3.4m in 2014/15. The last total figure for Elveden, correct as of September last year, was £11.3m, meaning a further £1.7m has been spent in the last eight months.
Tuleta cost £500,000 in the 2011/12 financial year, £1.1m in 2012/13, £1m in 2013/14 and £800,000 in 2014/15. Some £400,000 has been spent in Tuleta in the last eight months.
Earlier this year, a Press Gazette Freedom of Information request showed that 51 Met Police staff had worked on Weeting, 56.33 on Elveden and 16.66 on Tuleta.
In total, at least 64 journalists have been arrested and/or charged so far under these operations.
So far Operation Weeting has led to one journalist conviction for phone-hacking, after a trial, with a further seven journalists admitting the offence.
One conviction stands from Operation Elveden (of a journalist who admitted the offence). One trial is ongoing, with a further retrial of two journalists pending.
No journalists have been convicted of computer-hacking, although one journalist had accepted a caution.