I would hope your residency pays for this? If not, someone should go to bat that your program should at least pay for your choice of one of the EM societies (SAEM, ACEP, AAEM). Talk to your chiefs to bring this up; my program paid for us to be members of all three.
As far as should YOU pay for it.... its a personal choice and here is my take.
When it comes to policies, especially things political, there is power in money and numbers. Although I do not agree with 100% of the policy that ACEP sets or tries to influence, I do agree with many of them. I also find things like their journal (Annals), the scientific assembly, and the leadership and advocacy conference very rewarding and educational. Therefore, I do spend the money to join.
I like ACEP and generally believe in what the orginazation stands for, therefore I support it.....