It may be a truism that all submarine projects run overdue and over budget. A case in point is Sweden's A-26/Blekinge-class subs - now to be delivered in "2027-28". Another case is the Netherlands' Walrus replacement subs which might only be delivered in the 2030s.
Politicians, officials and companies regularly and safely under-quote how long and how much a submarine project will be, due to the factors below.
Submarine budgets run so long that politicians can claim they inherited the delay-cost problem. While politicians, officials and companies often quote "10 years" new submarine projects typically run for 15 years - from announced winner to first sub commissioned.
No single minister or person is held responsible because submarine building involves so many leaders and interests. This includes 15+ years worth of ministers for employment, regional development, high-technology, finance defence and whole of government prime ministers-presidents. Other leaders include heads of main submarine building company and or foreign country, heads of navy, of defence force and heads of materiel organisations. Over the course of a 15 year project even the head project manager changes.
Costs can always be re-explained as increasing due to inflation or that year 1 dollars vary from year 15 dollars. All of a project's costs might fail to be allocated to that project - intentionally and due to secrecy. Design changes due to failures to communicate, forgetfulness, changing technology and changing threat environments can always justify higher costs.
The public has a shorter memory than 15 years and submarine issues are so complex, with so many leaders and interests, that blaming a politician isn't possible.
Governments don't think in 15+ year spans. More like 2 to 5 years to win the next election. "Win the Next Election" being the first Law of Politics. One can't do "good things" if one isn't in power.
Would you believe Australia's 20+ year project to build its first nuclear submarine may result in the most "surprisingly" overdue, over budget submarine project in history?