German spending had been flat from about 1909-10 and GB's spending could go higher if needed. Don't confuse pre-war 'thats expensive' with 'we can't afford it'.
They did have an agreement of sorts from 1912: 8 Battle Squadrons to 5 and this laid out construction through to 1917:
__________1912___1913___1914___1915___1916___1917
Germany_____2______2______3______2______3______2______(14)
GB__________4______5______4______4(3)__4(5)_____4______(25)
Churchill wanted to shift one of the 4 1915 ships to 1916 (bracketed numbers - the Liberals were facing a General Election in 1915 and wanted to push costs to after the election).
The navy was to protect trade and foreign investment so money would be found if it was under threat:
Foreign investment was also accelerating in GB:
Which will back political support for the Navy.
The German navy will stay level through to the next Law Revision due in 1918 after which Tirpitz will have his 3 ships per year tempo set.
By 1920, the RN will be at about £60m per year while the Germans settle on about £30m per year. Far cheaper than the £38B that the warring nations spent on WW1.