The story is that Nokia invested about 8.1 Billion on Here Maps. Even selling at 3.2 is a huge loss. That being said, there is no solid information that Apple is even considering this offer. The rumour is that Nokia wants to sell and is courting Apple, among others. As you and others here have rightly said, Apple has invested a lot into its mapping app and this would be pointless, unless they work out a deal for "rest of the world" where Apple Maps isn't that great.