10W running 24/7 means about 7.3 kWh/month. In my area the average kW/h costs about $0.13 CAD
So a good rule of thumb is that every 10W 24/7 is about $1CAD/mo.
So assuming 30W for a laptop and 6W for a pi4, that means a difference of $29/yr. Which isn't a lot but isn't a rounding error either.