I don't think I use those neutral cards much. At least I haven't really seen many people use the endless ape card. Maybe they did but I haven't really paid attention to that.
Rebellion cards are definitely expensive. I think it has to do with the pack price being expensive. It's the most expensive one so far.
I have seen a lot of people using the endless ape, I just took the advantage to get it, seeing that it's a Rebellion card type that might not lose much value. The way it is, buying older generation cards is no longer viable.