To be fair to the guy we only know what the media has reported of what he said and I dare say all the figures are clearly explained somewhere*. The figure quoted in the media for overall savings takes into account the extra costs so I don't think it's entirely unreasonable to say the devices were bought for £30k each as it's obvious there will be other expenses on top of that given they're coming from Germany and will need to be adapted.
*Here in fact:
https://www.london.gov.uk/sites/defa...annon%20_0.pdf
5 Financial Comments
5.1 In accordance with MOPACs responsibility to deliver an efficient and effective police force and
secure value for money and the MOPAC Chief Finance Officer’s fiduciary responsibility to local
taxpayers the MPS have negotiated an in principle agreement to purchase three used Wasserwerfer
9000 water cannon from the German Federal Police at a cost of £30,435 each, or £91,305 in total
(€105,000 based on an exchange rate of €1 .15±1 .00).
5.2 Costs for transportation and refitting the vehicles to make them fit for purpose far London, and to
meet rigorous safety standards, are £42,300 per device, or £126,900 in total.
5.3 In comparison, new water cannon cost around £870,000, meaning that for each German device
purchased MOPAC avoid costs of approximately 097,000 or £2,391,000 in total.