> Getting memory from traditional allocators is expensive because freespace needs to be tracked.

If you've never deallocated then there is no free space to track, hence the cost of allocation is _mostly_ (per my above comment) affected by the amortized cost of deallocations. The cost becomes extremely apparent with GCs because a failed allocation is usually what triggers a collection (and subsequently any deallocations that need to happen).

Still, your comment goes into detail that I probably should have.