The reason is simple. Tankers are largely empty, coated steel structure, with some equipment on the weather deck and in the case of RFA huge amounts of accommodation, hangars etc back aft. No-one is more efficient in the world at churning out those sorts of ships than the Koreans. If you wanted to try and do that in the UK, you'd be looking at three-four times the price, if they could be slotted in in Govan (or potentially A&P Tyne).The real scandal is that it has taken approximately eight years and I suspect around £20M sunk costs to order four largish product carriers. Commercial shipping firms would have shot people for that sort of d1cking about. It took five years for people to understand a fairly simple concept - you can't get an "RFA-style" tanker on the commercial market, but if you pay someone to design it (well done this time BMT), a competent commercial yard will build it for you. The remaining three years have been spent bodging the tendering process.....However, good (if long overdue news) at last!