I don't keep track myself, but I never consider a game worth its msrp so it'd probably feel inaccurate to me. Kind of a false sense of savings to some degree like those sites that give you your Steam worth stats, since there's no way in hell most of the games I've bought are worth their asking price. If anything it'd make me feel bad about the hundreds of games worth $0 that I paid more than that for.
75% off #feelsgoodman though, dat dopamine release.
Maybe the reason I seldom play my recent purchases is so I don't feel that tinge of regret.
I know what you mean, though; there are very few games that I'd happily claim are worth their typical asking price, and of course many of the games I bought on sale I have absolutely zero intention of playing.
Edit: My interest in keeping track of my Steam-related expenditure is far less about how much I'm (comparatively) saving and more in regard to seeing how much I
spend wisely invest. Buying the new Daily rather frequently may seem slight enough, but over an extended period of time the cost is compounded, which isn't something you'd usually take particular notice of.