There were (and still are for the French Barracuda class) serious issues and delays in the just cancelled contract.
In Dec 2018, in the placing of the contract 2 years in the making there were disputes over the termination clauses in the contract. Australia wanted a 2 year delay or 25% cost overrun to trigger, Naval Group wanted 3 & 30% https://www.afr.com/politics/christophe ... 205-h18qmdhttps://independentaustralia.net/politi ... ment,12201
In 2019 this was reported: https://independentaustralia.net/politi ... ment,12201
An Australian government report Jan 2020, it indicated the first subs production would commence in 23 but not be in service until 2032. From the article
The contract is worth $605 million and covers work through to 2021.
So cancellation is probably around that amount of lost cost. [https://www.aph.gov.au/About_Parliament/Parliamentary_Departments/Parliamentary_Library/pubs/rp/rp1920/AttackClassSubmarines
A Jan 2021 article:https://www.abc.net.au/news/2021-01-20/ ... m/13074440
It hadn't gotten much better as reported in this March 2021 article, a quote from it follows:
Delays so far have pushed back delivery of the first Barracuda from the mid-2020s to the early 2030s and now to the 2040s. The latest missed date was finalising the critical Strategic Partnering Agreement which governs the entire project. This was due before last Christmas.
This was the next two year contract schedule, which was delivered 9 months late. https://independentaustralia.net/politi ... face,14846
An objective with contracts is to go with a parent design concept, thus avoiding a lot of startup issues, lessons learned, delays, etc. Well the Barracuda class submarine has only launched the Suffren, laid down in 2007 but launched in Aug 19, and still performing sea trials. It was to be in service in 2017. The 2nd boat, Duguay-Trouin, has not been launched yet, the 7th boat will not launch unti 2028https://en.wikipedia.org/wiki/French_submarine_Suffren
So the primary Barracuda class nuclear powered boat is running 4 years or more late, with 8 more years estimated to complete. The Australian Attack class submarine fleet of 12 was expected to be built over a 25 year period, building the subs in blocks of about 3 each.
So yes the Attack class order was already quite troubled.
Buying a variant with a completely different propulsion system of a submarine that has not been tested or commissioned yet sounds like a clean sheet variant of an clean sheet, tons of risk. The schedule of the program seemed to be moving to the right by a month every month. Costs soaring, work share being disputed, sustainment of 12 boats with the whole class having only 18 boats, with each major subsystem being a variant of others. In contrast, if by either the Virginia or Astute class versions, sustainment would be far easier - in particular if basically a Virginia class boat it would be a fleet of 40 or more. Just like with the F35, a much less costly option.
The Virginia class is built in 4 major sections, the propulsion plant would be a near complete section built in the US, the other 3 sections I envision being partially built either in the US or UK as it is very heavy very high strength steel requiring massive tooling. Work share where the Australians built components for either or both the Astute or Virginia class in trade could be done. Final assembly at the Aussie shipyard as well as fit out. A far more efficient scenario.