> I'd be extremely surprised if you could show that any feature or lack thereof actually costs you money,

Bad language design and semantics definitely costs money in the long term. For example, Tony Hoare refers to Null References as his "billion dollar" mistake. The verbosity of Java before sophisticated IDEs would also have cost significant time and money. Java is improving significantly (and arguably was never as bad as say JavaScript or PHP), but there are some legacy decisions that will be very hard to change; and so improvement can only ever be incremental.