Absolutely! Bow out gracefully and offer the B-day girl a lunch at a later date. If they're REALLY your friends, they'll understand. You've been through so much in the last while - and this whole party thing sounds absurd! Freezing in the middle of Detroit crammed together? Well that sounds like a ball, doesn't it? Besides $200 plus food plus a gift? I don't think so!!!!!!!!
Do what's best for you, and then thank them for understanding and respecting your decision (whether they do or not is their problem.)
-------------------- Formerly HanSolo. IBS, OCD, Bipolar, PTSD times 3.