i have not played Rebellion but its rather popular around here. One time on friday we literally had six games going at the flgs, it was kinda funny to see BOARD GAMES hog the tables for once. Ive observed and read the rules, and it seems really dull to me both because its semi-static in whats going on each game independent of the player's actions and it got a LOT of stuff to track.
Also the strict 2 player format bugs me. Its 4player rules are not 4player, its 1v1 with a stat tracker. Ascendancy is planning to goto 10 players since theres 10 turn order cards in the box. I doubt i'd ever get that many people at the same time let alone have the SPACE for it because even just the normal 3player game can easily hog up a large table quickly.
Ascendancy's price is more in the work that went in the rules than anything else. Board games in general are kinda expensive because of that, you have to word everything in a way that theres no confusion. And in a 4x style game, thats not easy. I play 4x games all the time and ive never started playing one with prior knowledge on what i was doing, but because it was a computer game i didnt have to worry about not knowing the rules. Cant do that with a board game.
Also FFG is a bigger company so they can afford to have it be a bit cheaper lol.