Your calculation further reinforces my thought that anything that has been reported regarding Mogami for our navy so far are mostly still educated guesses at best.Noting from notable sources (like wikipedia and others news media, including AH videos) said that our 6 FREMM + 2 Maestrale cost € 4,1 billions or around $ 4,6 billion and the Four 30FFM said cost about ¥300 billions ($ 2,7 billions)
Lets take it one by one
both 6 FREMM and 2 Maestrale Cost € 4,1 billion, its not fair if we divided the cost per ship equally because we have 2 used ship, so if we assume the cost of 2 maestrale is roughly €150 mln each, means €300 millions both, we will have € 3,8 Billions for the 6 FREMM, means € 633 millions ($ 715 millions) each, and thats reasonable price for Italian FREMM
but for 30FFM said it cost for ¥300 billion ($ 2,7 billion), divided to 4 equals to $ 675 million each
well according to this news
Japan’s New Mogami-Class Frigates Show What The U.S. Navy’s Littoral Combat Ships Could Have Been
The frigate's design attributes-speed, small crew size, support for unmanned vehicles, and anti-submarine and counter-mine capability-also guided development of U.S. littoral combat ships. The design Japan settled on is somewhat larger, a bit less expensive, and more versatile and heavily armed.www.forbes.com
"The Japanese Maritime Self Defense Force (JMSDF) eventually plans to procure a total of 22 of the stealth escort frigates (also designated “destroyer escorts”) built at a pace of two per year, at an estimated cost of 50 billion yen ($467 million) each"
sure we see the price jumps from the domestic price to the export price,
im not sure why
also im not sure if that all the costs is included with the armament it needs or not.
We can assume anything as well, especially regarding to more than $100 million difference between the quoted and your calculated prices.
However, this is my guess: If the deal got through, we'll probably get four Mogamis built in Japan and an option for two more to be build in PT PAL.