This is why characters like Boco have disappeared-unable to keep afloat, Hatt has been selling some of the more expensive engines off to other railways. This is also why certain new characters "arrive on the island" or are "on trial" but are never seen or heard from again- they were on loan to the Sodor railway and their own managers take them back after a few weeks. The Fat Controller can only afford to buy and keep extremely outdated models, such as Emily. The Fat Controller hasn't told the engines yet as he wishes to keep their morale up and have them working at peak efficiency.