If 77% of power can come from rooftop solar when far less than 70% of people have rooftop solar, then you'd expect prices to rapidly decrease for consumers. Unfortunately retailers are now able to sell power that get access to almost for free (solar feed-in payments have been heavily decreased it looks like). This will only further incentivise people to get their own panels, increasing the grid instability. It is actually in the networks best interests to put downward pressure on prices in this case, otherwise they'll need to front the costs of managing an unstable grid.