The TSR Marvel Super Heroes game did something similar. Heroes accumulated Karma points, which could be spent in a pinch to adjust rolls on the % resolution table, or could also be saved up to increase attributes, powers, or invent new "power stunts", special ways of using your superpowers. If you killed someone you lost all your unspent Karma, which was a pretty good incentive to heroic play.
I once ran a game with the 1gp=1xp rule, and the players still took around a year to hit lvl.4 because they avoided taking treasure and going into dungeons.
I agree I think spending money also should count for xp as well like one of my players wanted to make a shrine, I was totally going to give them xp for that.
I like it too, expecially when getting large amounts of treasures.
I played ADD1 during six years when in high school, we never used that rule, which we ignored totally: during that time, I think that only one of us got to the fifth level, and it was considered an achievement. We did not understand for who 10th level module were written for
