I have some friends at AirBnB and I've heard it's much more modest, like $300/yr or something. My experience with these type of "dogfooding" credits is that companies are much more generous when they're smaller, so it could be that older employees get more than newer employees.

$2k/year ($500 every quarter)

That makes sense. $300 is enough to cover Airbnb housing costs for at least a few days in pretty much any location around the world, so they probably still get value out of it.

I think it's a 500$ coupon at the beginning of every quarter.