It is not only about absolute number of objects created, of course. It is also how long they kept and how often the are changing.

Immutability gives simplifies everything including incremental, parallel GC and hence reduces the pauses for GC.

This is the big idea behind Clojure and Datomic - immutability makes everything simple (less complex runtimes) and even more scalable (share nothing means no locks, mutexes, busy waiting) and in the case of Erlang - fault tolerant (strong process isolation - no threads with shared stack or any writable data).

What is funny - everything has been well-researched and right principles formulated by Erlang team decades ago, and the resulting product just works for telecoms.

The two fundamental principles they described are 1) Posix threads and fault tolerance does not match. 2) Imperative code and GC does not match. While Golang, Lua or PyPy are trying really hard to disprove the second principle, Java is an existential proof.