Well, except for those of us who think it should be...
Marvel Preview 7 - 'First Appearance of Rocket Raccoon' Summer 1976
IH 271 - 'Second Appearance of Rocket Raccoon' May 1982
My point is Marvel Preview #7 is the first appearance, although a magazine. Some people pimp IH #271 as the first comic book appearance of Rocket Raccoon (with a cover appearance). However, MP #7 is more valuable. Yet Marvel Super Special #16 (magazine) is the first appearance of Boba Fett, but Star wars #42 is more valuable. The same logic does not apply. Yes, the market will decide, but sometimes the "rules" are as clear cut as you think.
This surprises you why? Logic in our hobby is a purple unicorn...