Interesting points, I agree with the statement to announce where the RP is, yet I do not quite agree with increasing the cost of land, for increased land costs could negatively impact groups that are looking for a place of their own yet do not have much in the way of minas (Like the halflings, for example)
If the costs of land were to be increased, maybe it could be that only the cost of tiles are increased? While land charters do spread out RP and can take away from the RP in cities, the main issue is the metric ton of baronies, forts, strongholds, etc that are often spread out about a nations lands.