Not if they have the right density. I think their business model is viable at scale.
Assume they pay their pick-up guy $20/hour. Each customer is paying $5 for 12 pickups = 60 cents a visit. To break even they will need to do pick-up 33 mail boxes/hr. This seems like a lot in a suburb but it's possible in a dense city. They will probably need to tweak their model but it's not unreasonable.