It looks like your quote is to upgrade the meter and main panel, and install new breakers for the AC and water heater. Which is good, and sounds necessary, but only the first step to modernizing the home’s wiring. Upgrading the grounding system means the connection between the main panel and the earth, which usually means driving copper rods in the ground.
Now, if the wiring between the main panel and the outlets is serviceable, he can connect those at the panel and you’re good. But if you don’t have grounded plugs currently, you should run new wires to each outlet and remove the old wiring. This is a big job behind the drywall in every room, thus doubling the quote you got.
Edit BTW the $2000 quote might sound high but it’s fair. For something that can easily burn your house down if done incorrectly, don’t go with the $500 guy.
It’s this. All the tech companies overexpanded during COVID when free investment money was everywhere. Now they’re all over staffed and want employees to self select out of employment rather than announce widespread layoffs. Meanwhile ruining life for everyone who can’t afford to quit.