'Cost today' to Home Assistant via local MQTT
I have Home Assistant pulling in info from our Glow IHD/CAD on a SMETS2 meter. This all works nicely - I can see our daily, weekly, monthly and total import values (kWh), along with daily standing charge and unit rate. However, I've never been able to pull today's actual financial cost across. When on a fixed tariff this would just be a simple calculation, but we are on Octopus Agile so I'm foxed as to how to calculate daily cost across each half-hourly tariff. It appears the simplest option would be to import 'Cost so far today' from the Glow, but it doesn't seem to be exposed as a sensor on MQTT/Home Assistant.
Is there some clever way to do this, that I'm just not familiar with, or does it all boil down to half-hourly calculations in Home Assistant every day?