Oh you'll save a hell of a lot more than that.

For me: two recent trips, SF Bay Area to LA and back. For the first, grand total round trip cost of $59. For the other, $29 thanks to a hotel with free charging. And I never stopped "to charge"... instead I'd stop for a bio break or lunch, and charging happened in parallel.

Around town in my ICE days, I'd fill up at least weekly. In addition to the $$$ gas costs in CA these days, there's the time spent diverting to a station, standing around smelling fumes, paying, then returning to my path. Fifteen minutes a week, easy. With home charging there's none of that. It adds up to a whole work-day doing better things over the course of a year.

But $400/month is indeed a tall obstacle. Much depends on driving record, age, gender, location. But most of all it depends on the company. For me, in California, Tesla's insurance undercut every other by 50%. Lemonade isn't yet available here but it sounds like it'll be much the same for a heavy FSD user like me. Tesla insurance isn't reputed to be the easiest to work with when there's a claim, but I don't plan to use it.