How come Rocky wasn’t amazed he was going to get 150,000?

Regarding the money, I think Rocky was one of those people who didn't really care all that much about money. He was preoccupied and worried about the fight to think about the money at that time.

I think he was somewhat "star-struck" by Apollo in the movie. If you watch the scene where their press conference was on TV, Rocky pretty much lets Apollo play him as "comedy relief" in a way. Rocky acknowledged a couple of times in the movie that Creed "is the best." But I love the scene where Rocky does acknowledge that Creed's behavior at the press conference (among other things) did bother him (after initially denying it at first). I think he started to see Apollo in a different light after that.

I think maybe he was amazed about the money - they just didn't make it a focus of the movie. For Rocky, it was all about getting a shot at the champ. Consider the scene when he was in Jergens office, he asks for the appointment card back from the receptionist, such an odd thing, but perhaps he already cherished having this as a memento? Not sure, just a guess. And how he assumed they were asking him about sparring, and finally when Jergens asks him to fight the champ, Rocky's knee-jerk reaction is simply "No". Clearly he was way out of his element, not even having to meet Apollo.