Playstation started with a SRP of $49 when it launched in the US in 1995. Sony dropped the SRP of first party titles to $39 in 1997, several years before PS2 launched. PS2 launched with games back up at $49, and then Sony followed Microsoft's lead and upped it to $59 for the PS3. So if you look at a narrow window of time, you see games going $39 -> $49 -> $59, but that doesn't give the full picture. Throw in inflation, and the increased costs, and games are shockingly inexpensive.

Sone SNES cartridges were even more expensive: Chrono Trigger was $79.99