GOG is selling selected DRM-free games from the last 30 years at up to 90% off the regular price, which means something will go for 59 cents!
The catch is that you have to be there when the game goes on sale.
They started at 1983 with the Zork games and they're up to 1987 now with Space Quest 1, 2 & 3.
You can determine how long the game(s) will be for sale by adding or subtracting a second.
So pick your favorite game/year and see what comes up!