Apple compared the M1 Max to a 3080m. 4x the GPU cores and up to 8x the memory makes a difference, and it wouldn't be at all surprising to see that their numbers are accurate.
No one has explained what you got wrong, so in case anyone reading this is still confused, Apple compared an M1 Max to a 3080m. An M1 Max's graphics card is ~4x as fast as an M1.
In the current market you can buy a MacBook Air (an entire laptop computer) for less than buying just a midrange GPU.