Singapore's Defence Ministry (Mindef) signed the purchase deal with TKMS on November 29, 2013 to buy two the 218SGs. The contract was likely to be worth more than 1 billion euros (US$1.36 billion).
In hindsight this website's November 13, 2013 article http://gentleseas.blogspot.com.au/2013/11/germans-sinking-kockums-swedish-sub.html was an indicator that HDW winning the Singapore order was suspected by the Swedish and German media. Singapore's 218SG decision is clearly a blow to Kockums and to Sweden's Navy (which would rely on foreign sales of Kockums subs to lower unit costs of Kockums subs). Unless the Swedish Government or a Swedish firm buys back Kockums Sweden might be forced to buy its future submarines from HDW or at least TKMS owned Kockums. Also link with Saab Being Subsidized to Buy Back Kockums? of March 4, 2014 http://gentleseas.blogspot.com.au/2014/03/saab-being-subsidized-to-buy-back.html .
For Singapore there is some continuity buying customised submarines - from customised Kockums Archer and Challenger Class to customised HDW 218SG class.
I suspect HDW 218SG will be an enlarged evolution of the HDW 209, 212 or 214, perhaps like Israel's HDW built Dolphin 2s. The HDW 218SG may be larger - between 2,000 and 3,000 tons (surfaced) see http://gentleseas.blogspot.com.au/2013/12/the-hdw-218sg-probably-3000-tonne.html . Given the expected 218SG delivery date of 2020 it is unlikely that the 218SG would be radically enlarged to 4,000 tonnes (HDW 216 Class). A 4,000 tonne design would probably take longer than the seven years to develop (2013-2020). Also the 218's purchase price of around US$650 million each implies an existing design rather than a radically new 4,000 ton (surfaced) 216 which would be far more expensive.
The two 218SGs, together with two existing Kockums Archer Class submarines, will replace the four ageing Challenger Class submarines, built in the 1960s and acquired by Singapore in the 1990s, which will be progressively retired from service. This follows Singaporean Defence Minister Ng Hen's comments in March 2013 about Mindef's plan to replace the Challenger submarines.
For some Comments made in September 2009 which envisaged market distortion between HDW and Kockums see this website's earlier article on Singapore's Archer and Challenger Class submarines at http://gentleseas.blogspot.com.au/2009/09/singapore-submarine-development.html .