I'm not sure the bolded is completely true, though some sports card mentality has begun to permeate the hobby. What I do agree with is the comment a couple of pages back, that stated that once the hype train has left the station for a certain book, it's pretty tough to go backwards.
Right now, that certain book is 7.
Then give a modern example of a non-first appearance that outsells the first appearance where the two books do not have a significant gap in print runs.
The Walking Dead 132 and 138. Alpha is seen inside the book on #132 and on the cover of #138. It has been an seesaw battle as to which book is "the" book depending on the day. BigClutch stated that #132 was the issue. There isn't someone who would be a bigger authority on the subject short of Kirkman. Still, the books bring about the same $, day in, day out.
There's a few gray areas. Kamala Khan. Superboy will be a fun one. Godspeed may as well.