Thanks everyone’s input! To sum things up:
Downloading files directly from the host’s link will charge your own transfer quota, which is unless the host is a pro user, and has the “share quota” setting turned on.
For Pro users, if you would not like to have others depleting your transfer quota, set “Grant your transfer quota to users downloading your links” to 0% in settings under “Transfers” tab.
Free users should have no worries as they cannot share transfer quota with others.