Vans appear to be slightly more expensive but not outrageously so (and honestly it's not at all uncommon to get a free upgrade when you book the economy car).
As for insurance, why would our hypothetical family need to get insurance? Surely they already have it, if they have a car that they drive.
I'll grant you that insurance isn't necessary (or even advisable), however plenty of people feel more secure getting the (very expensive) protection given the risk of driving an unfamiliar car to likely unfamiliar locations.
Still, glad to see prices coming down. I paid $80/day for 3 days in June and $75 (after a discount) in July.
(It's outside my risk tolerance to reserve an economy car and gamble that I will arrive at the airport to be delighted by a complementary upgrade to a vehicle large enough to transport my party.)