I recently came out with this article regarding ATA costs and how VoIP resellers can address the issues that arise from this. The gist is the different schemes available to VoIP businesses -- which is best for them, depending on their financial situation.
For VoIP resellers with ample funds, the best way to go is the ATA box rental scheme. This way, the VoIP reseller minimizes the impact on the user's wallet, keeping their VoIP service affordable.
For VoIP resellers that are lacking fund, the best way to go is to require immediate purchase of the ATA equipment, either from them or a third part supplier. They can just help the user when it comes to choosing models and suppliers.