Get Size of Folder Containing Hardlinks (like Time Machine Backups)
The answer, partially assisted by the comment above, is to use du

Specifically, 
du -hs /path/to/folder/i/want/to/get/size/of

This counts hardlinked files only once. This is the parent folder of my hard-linked backups. So Finder tells me ~322 MB but du tells me ~171 MB. I don't think the 1000 vs 1024 issue is taken into account, but it's certainly close enough for my needs!