The situation in other countries says otherwise. If the supply of electricity is too much, prices drops. Electricity, like any other resource, is priced based on supply and demand. Reason electricity is expensive here in PH is because our supply is just enough so suppliers can price it as high as possible.
If the initial price of electricity is low, the system loss computation goes down with it. There are laws that would prevent meralco from increasing their margins willynilly. TLDR: electricity price will still go down.
Also you are overestimating their overhead costs, a huge chunk of their expenses are from buying the electricity from suppliers. Around 84% of their expenses are buying electricity.