I think if the cost is a little more than current storage services, there will still be a market for this service although much smaller. If this network can provide a cheaper option then this service will take over. Even if the cost of having storage on this network is significantly higher than other services there will still be a small group of users who will continue to use this and since this is an open source and community hosted network it can adapt over time to potentially reduce cost by possibly reducing the amount of redundancy or improving the algorithm in another way to make it more efficient.