LoL ! The value isn't retained in the network.

It's bled from the network and goes straight into masternode pockets.

In accounting terms, "retained profit" is profit that is not paid out in dividends or costs. In Dash, coins that are paid to masternodes are a COST to the network. Their value is not retained. On the other hand the value of coins that are paid to miners IS retained by the network because their revenue is used by miners to bid up the price in a competitive race against other market players attempting to acquire coins from the primary supply.

The electricity cost is therefore not an overhead, it's simply the bidding currency of a trustless market. Like you need to convert $USD to Euros to buy a coffee in France, you need to convert $USD to Kilowatt Hours to buy a coin from the primary supply.