Frugality can be a virtue, but I think many people think too narrowly when they focus on nothing but the bottom line. Based on the national average hourly wage of $23.82, one minute of your time is worth about forty cents. If time is money, here are a few things that are probably not worth wasting much time on:
Splitting your bill at a restaurant. Unless you just split the amount evenly, you're losing $1.99 per 5 minutes of arithmetic and arguing. Sure, if you're going out for dinner and drinks, you might get more of a return than that, but if it's a lunch where you're all ordering things of about the same price, it's probably not worth the trouble to figure out who got what, and how much each of you should tip.
Picking up loose change = 5 seconds of your life, or about $0.03. In other words, a penny isn't even worth the time expended picking it up and putting it in your pocket.
Haggling over anything that costs less than about $50. Unless you talk the seller down more than 4% in 5 minutes, you've actually lost money on a $50 transaction.
Looking for "bargains" instead of shopping based on quality and features.
Is it really worth looking at more than 2–3 websites for a price comparison, much less going to several physical stores? How much of a bargain did you get when you include gas and travel time? On a few big-ticket items, it might be worth doing extensive research and checking several stores, but it's probably not worth it for most things.
The most extreme waste of time that I can think of, dithering over buying iPad apps, was hilariously lampooned by The Oatmeal. A $0.99 app only deserves about a minute of consideration before buying or rejecting it, not the several tens of minutes I've seen people spend looking at multiple reviews and reading blog posts before making a decision.
What's almost unbelievable to me is that some people take the time and effort to write a review on the iTunes store about apps, saying that they'd like to buy iHornswoggler Extreme HD (#1 in in-app purchases, by iReamU Good!) but think it's too expensive for what it does. That means they: looked for an app that would solve a problem for them, read some reviews about that app and other similar apps, thought about buying that app, rejected that idea, signed into the iTunes store, wrote a review about an app they haven't used, and presumably gone on to waste even more time thinking about buying a different app.
Just writing a YouTube–comment quality review ("dont leik ths appp, 2 xpnsv, u suk!!!") eats up at least $0.99 worth of time. But I guess logic isn't a strong suit of someone who would waste that much time on pure negativity.
My wife pointed out that, for single people, cooking is often not worth the time. You will likely waste unused ingredients — unless you plan your menus well and stick to that plan — since most things are not sold in single-serving amounts. If you also account for the time spent preparing and cleaning up, a home-cooked meal for one easily equals the cost of eating out at a family-style restaurant, possibly even the cost of a meal at a mid-level restaurant.
Some people criticize low-income families for eating at fast food restaurants, saying that it's a waste of money when they could be eating cheaper by making their meals at home. Counting the time saved, it can actually be a good use of resources.
Aside from the separate problem of there being few or no grocery stores in many poor neighborhoods, there are hidden costs in setting up a kitchen that most middle-class people take for granted. How can you buy a refrigerator when you're struggling to pay rent? Poor families might have to choose to go without power for a few days if they have to pay for something that has priority over a utility bill, which means that anything that needs to be refrigerated — or worse, frozen — will become expensive garbage instead of cheap food. "Wasting" a few dollars eating at McDonalds starts to look pretty reasonable in those circumstances.