Float objects also require, as do all Python objects, space to hold a
type pointer and a reference count.  So each float object requires at
least 16 bytes (on most 32-bit boxes, 4 bytes for the type pointer, 4
bytes for the refcount, + 8 bytes for the float).  So 100 million float
objects requires at least 1.6 billion bytes.

It is a gc issue in the sense that the float-object free-list is both
unbounded and immortal.  For that matter, so is the int-object
free-list.  This has been discussed many times over the years on
python-dev, but nobody yet has a thoroughly attractive alternative.