If you analyze expenses for software projects of 1960-80ies and compare them with recent years, you probably see that the most expensive item now is at the bottom. The most costly thing used to be hardware. The not so expensive - developer's time. Now it's the opposite - the equipment is cheap, and the software developer's salary is the most expensive thing. Of course, that does not apply to every single case, but for the majority of projects, that is true.

Immutability by default (baked into the language), offers enormous benefits, and increases programmer's productivity, it simplifies many things, especially concurrency and parallelism. Languages like Erlang and Clojure are good examples. The price you are talking about does matter. But very often, the benefits outweigh the small cost.