For almost all users, Places will have a negligible impact on data usage. Updating all of your Places geofences and campaigns uses less data than one update to an in-app campaign.
If you were to create all 10,000 geofences and a lot of campaigns, the update would be around a few hundred KB.
To get a better background on Places & geofences read up on it here as well as more information on Messaging with Places.