The output is floating, it's not connected to earth.
Body resistance varies wildly, both from one individual to another and depending on how wet the skin is, it's also non-linear, so it becomes much lower as the voltage increases, but yes, you won't get anything like 2A from 24V.
Not that it needs to be, 500mA is enough. The lowest recorded fatal voltage was 42V AC (and the highest survived 230kV), but the body is about 3-4 times more sensitive to AC than DC, Wikipedia doesn't say why. I've survived a 240V AC shock from arm to arm across the chest.
When I bought my HiFi I could feel the leakage current from the front panel buzzing on my fingertips even though it was well within spec, but I can't remember what that limit was now.