Good question, lets have a look.
The @fdroidorg repo on our main mirror currently has ~110GB and the archive has ~384GB in size. So all in all it's manageable.
At this point we'd like to thank fau.de cyberbits.eu tetaneutral.net lysator.liu.se and rcac.purdue.edu who kindly mirror our repo. Those mirrors help a great deal reducing traffic cost.
chaos.social – a Fediverse instance for & by the Chaos community