Both posts assume you know the price gap before deciding. That's the missing piece.

You can't evaluate "is $8 savings worth 8 minutes" if you don't know the gap exists until after you've parked. The decision requires checking prices before leaving — which most people don't do because it costs effort.

Also: "$8 cheaper overall" hides that savings are concentrated in 2-3 items. If those items aren't on your list, the gap is $0 for you specifically.

The real problem isn't routing or time-value. It's that you need two pieces of information (current prices + your list) before the calculation means anything. Most people skip the lookup and then can't act on the tradeoff.