My $/hr equivalent from my salary is much more money than I could save by doing practically any other task. By the $/hr metric, I should probably be outsourcing every activity besides my job, sex, and managing my investment portfolio. Since I work less than half of my waking hours, the absurdity is magnified by the fact that it would bankrupt my despite being optimal according to that simple $/hr rule.
There are two underlying problems with that simple logic. One, you're comparing to work even though that's not your replacement task for what you might outsource. You're doing that because its easy to quantify, but quantifying the wrong answer is counterproductive. Two, you're assuming that the task that saves money produces no other value, which might be the case if you were saving money by sitting in a dark room staring at a wall, but activities like cooking are at least a little more interesting than that.
So here's why I cook my own meals: for those 5 hours a week I am cooking/shopping/planning meals, I would otherwise be doing a little bit more of what currently gets squeezed out of my schedule, in little chunks throughout the week -- probably reading. I prefer reading to cooking, but only by a little bit. I would be willing to pay $20/hr to read a good book instead of being locked in a dark room staring at a wall, but only about $5/hr to be reading instead of cooking a meal of my choice. In addition, reading a good book requires some uninteresting time spent driving to the library or it costs me about $2/hr in book purchase costs, so realistically as long as cooking is saving me at least a few bucks an hour I will do it myself. It's just not that unpleasant an experience for me.
In contrast, I do pay somebody to maintain my yard -- I enjoy that task alot less than cooking, and I do a poor job of it compared to a professional, so even though the dollars saved per hour is greater, it's more costly to me in terms of personal enjoyment, so the $$ per personal enjoyment comes out cheaper to outsource yardwork than cooking.