It seems to me a local church has a maximum reasonable size of 22501. I'm basing this off of the Dunbar number and a simple idea of structure: one bishop, 150 priests, who minister to 150 laypeople. This is a maximum number; I think it would actually be tough to minister to 150 people, especially since I think a big part of this ministering is confession in a very orthodox sense.
One of the greatest complications is that the priesthood is at once highly important, but also appears to need to exist at a population level wherein most would not be able to derive their sole source of income from their vocation.
But in terms of God's economy, and our need to conform to Him, we would be wealthy.