There aren't separate charges for separate lanes. There's a set of express lanes, which get a dynamic per-mile charge based on conditions, and a set of normal freeway lanes which cost nothing.
The intent is to set the express lane pricing to a level that keeps their speed at 45MPH or more. The free lanes just do whatever.
In this case, the slowness was based on weather conditions and plow trucks not because all the traffic was on express lane and all other lanes were empty. Clearly, their algorithm needs to take road conditions into account when creating this prices.
I didn't read this as a premium to use the express lane or only allow rich people to get home, just an unintended consequence of a beneficial program finding an edge case.