OpenBSD:
[x230](0)(work)$ ls -l test.txt
-rw-r--r--  1 sdk  sdk  75600 May 12 21:25 test.txt
[x230](0)(work)$ du test.txt
152     test.txt
[x230](0)(work)$

FreeBSD (ZFS)
root@top4:~ # ls -l test.txt
-rw-r--r--  1 root  wheel  75600 May 12 21:25 test.txt
root@top4:~ # du test.txt
5       test.txt