My 3 19.2kW EVSEs load balance together, so the total draw on the grid is never over 19.2kW. When 2 cars are charging, each is only allowed 9.6kW. When I need faster charging, I just unplug all but the EV that needs to charge faster (or make sure the other ones are not charging via a phone app). The grid doesn't care if I charge 2 EV's at 9.6kW each, or 1 EV at 19.2kW.
The grid does care. You're charging for two or three hours, and then not using that power for 21 or 22 hours. That means generating capacity has to be brought online to cover that load. And when everybody does this all at once when they get home from work, it creates a significant increase in generating capacity at a time when solar is unavailable, etc., and because that load is brief, you don't get to use clean base load power, and end up spinning up peaker plants (likely natural gas).
The argument on the weight is just silly. The on-board-charger is the exact same size and the weight is listed the same between the 2 parts, I suspect the sizing up of the MOSFET transistors, or maybe adding a couple, doesn't add any significant weight. I'd be willing to bet that you can't tell the difference between the 11kW and 22kW versions by just weighing them, especially if you just took it out of a live system so it may have some liquid coolant in it left.
I'm kind of surprised by that. Unless I'm misremembering, Tesla's high-current charger used multiple modules in parallel for efficiency reasons — I think two modules for the standard charger and three for the high-power charger. Their superchargers do the same thing for the same reason. I kind of assumed everybody did it that way.
Offering to replace my 3 AC EVSE's with set of load balancing HVDC chargers, installed, it not going to be $3K. $3K is a cheap Chinese hardware only. Higher quality 20kW HVDC run $10K+.
No, $3k is the off-the-shelf retail cost for a basic 22 kW HVDC charger. Cheap Chinese hardware for 22 kW HVDC from Alibaba starts at only about $1,000.
Also, I think you're massively overestimating the labor costs here. Swapping one 3-phase charger with another in place means turning off a breaker, removing several wire nuts, unbolting the old one from the wall, figuring out how to fasten the new one to the wall, and putting the wire nuts back on. It involves nearly zero actual wiring work. It should cost only slightly more than replacing a bad receptacle ($80 to $200). If installation is over $500, I'd be absolutely shocked.
So for a basic version, probably more like $1,500 installed. Getting one with better firmware that can do load balancing would cost more, but not an order of magnitude more.