Most of my SQL servers Eat up 90% to 95% of its memory, my average SQL server build is between 64GB to 512GB of RAM. I am having a hard time setting up alert thresholds based out of percentage. no one cares if you eating 95% of memory because my server builds are huge

can anyone give me point on how to setup alerts based on high memory consumption server? the OS only need 4GB of memory I think