Probably because back then rom chips cost a lot and no game companies were making giant profits. Even Nintendo wasn't raking it in like now. Video gaming back then was such a mosh pit of weird shit like Atari, Turbografx, a half broke Sega, and the industry was the fraction of the size now.
Now, game companies are raking in tons of profit due to digital being cheap form of distribution (no inventory or packaging) and mtx fees can make any game a big money maker.
Any big company claiming they need $10 more per game for survival is lying. It's purely about profit boosting.