That’s correct and that’s what you need. Process 3 needs to be an adjustment for “price per unit” and that will arrive at the “current hourly running cost” which you can save if you choose but to get an accumulating “total spend” you should use another “power to kWh” process.
Think of the “power to kWh” process as a “flow rate to running total” process with in-built x0.001 scaling (the scaling you will need to counter in your unit price adjustment0.
eg a 100w load at unit price of 15p per kWh after 30mins would look like this
log to feed
power to kwh
kwh unit price
power to kWh
or if you want to see/save the current running cost