Dale Mitchell Hurley, http://risks.io Founder
Wasting money is a fluid concept since money is a fluid concept. As the benefit-to-cost ratio is very different to everyone, and costs include many more aspects besides money.
Consider an extreme situation where you have all your money in the bank and you are starving, you arrive at a high-price restaurant and you can purchase a meal to fill your stomach, that high bank balance means nothing. Consider a more realistic situation, you work hard all your life and scrimp on everything and while your bank balance is high, your life is boring, you haven‘t "wasted" money but you have wasted your life.
Maslow outlined a hierarchy of needs. These needs explain motivation. One must adequately satisfy the lower order needs before higher order needs. This is why money and wasting money is a fluid concept. A lot of the other respondents have ignored that every single person is in a different situation and their needs differ. If lower order needs are taken care of then anything I spend money on to satisfy the next higher need is money well spent.
Going back to the OP‘s example: "For me spending on buying junk food at multiplex counters is waste of money. They almost rob us." So why is this a waste of money or not?
I get that there is a big markup, since they have to cover their costs. They may inflate the price to 5 times the cost at the supermarket, yet we still consume the products with little thought. Why so?
Because we value the convenience, you may feel this is a waste of money, though to others it maybe worth the extra cost to save them leaving their date and appearing as cheap. Taking a date to the supermarket would pretty much guarantee there will not be another date. So buying from the candy bar may lead to a lifetime of happiness. So is it really a waste of money?
On the other hand, you might not have enough money to buy your lunch for the next week so it this case impressing the date might be a waste of money.
It is all relative. When I was single, to me it is a very good option, to you it might be a very bad option.
With the iPhone as an example, a lot of people claim this to be a waste of money. This is simply not true in my situation. In Australia phone services are massively expensive as our population is spread out. My parents and grandparents make a lot of calls every month using their landline. Their landline bill exceeds the cost of my iPhone, my wife‘s iPhone and our internet connection combined since we make 0 (zero) phone calls via our landline. In Australia the mobile operator provides the handset and includes pretty much unlimited talk and text. So in our case the iPhones are much cheaper than landlines. We also are constantly using our phones for entertainment, so again the value of the phones is greater than the basic features. So are we wasting money?
Say you have two food options, the first option is half the price of the second option. Both options will fill you up. The first option is ordinary. The second option tastes amazing and you will think about this option again and again. Lets say both are chocolates, since chocolate is amazing and there is cheap and very expensive chocolate. I can easily afford both. I will be disappointed with the cheap chocolate. So while the second option is double the price, the first option is going to lead to buyers regret and disappointment so the cheaper option is the waste of money. The same concept can apply to anything, e.g. computers, I owned quite a few laptops (as apart of my job) and nothing brings me more job than my MacBook Pro, for quite a few reasons, one being vanity which is okay because to me the vanity value is worth more than the cost.
Now consider Tim Cook. Say he wanted a private jet. He could fly economy on a budget airline. However a private jet will mean he has internet, phone, and can conduct highly confidential phone calls. If this means the extra benefit exceeds the cost than it is not a waste of money.
Consider someone with $USD100M. Spending $USD50K on a watch will give them a lot of satisfaction and they are not going to miss the money. Spending $5K on a watch may make them feel cheap and get regret (this is a form of cost) the purchase so the $5K would be a waste of money.
Bringing it all home, if you derive more benefit from a purchase than the total cost you have made a wise purchase. If you derive less benefit than the cost (including other forms besides money) than you have wasted your money.
Dale Mitchell Hurley, http://risks.io 创始人
浪费金钱本身就是一个不确定的概念，因为钱本身是个不确定的概念。每个人的收益率是完全不同的，而且花销除了金钱还包括许多其他的方面。
试想这样一种情况，当你饥肠辘辘时拿着你银行账户上的所有的现金，来到一个昂贵的餐厅然后点了一份豪华套餐填饱你的肚子，那么吓人的银行余额就显得不那么重要了。再试想一种现实中的情况，你一生勤勤恳恳努力工作在所有事情上都精打细算，使你的银行余额很高，但是你的生活却很无聊，那么你并没有浪费金钱，但是你却在浪费你的生命。
马斯洛描绘了人类需求的分级。These needs explain motivation.（这句不会翻）。 一个人在满足他更高层次需求前必须充分的满足它的低层次的需求。这是为什么金钱和浪费金钱是一个模糊的概念。许多答主都忽略了每个独立的人在不同的情况下他们的需求也是不同的。如果低层次的需求已经被顾及到了，那么其他我们所花费在高层次需求上的金钱就是值得的。
回到OP的例子上：“对我来说在货柜上购买许多垃圾食品就是浪费金钱，因为它们几乎是在抢劫一样”（物品可能根本不值，就像在明抢，但是因为你贪吃）。所以这就是在浪费金钱么？
我认为这其中可能存在很大的利润，因为它们占用了我们的闲钱。它们可能是我们花费在超市购物的5倍价格还多，我们又不能为消费这样的物品带有任何想法。为什么要这样呢？（这段翻译的不知道想表示点啥）
因为我们消费了舒适感，你可能感觉这是一种金钱的浪费，但是对于其他人来说，它是值得的额外花费，因为可以帮助他们节省出时间去约会或避免花时间去抢购超市打折品。单独花费一个休息日去超市购物一定会让你失去一个可以自行安排的时间。所以从便利店（candy bar不能翻译成糖果条吧）去购物可能会带来生活中的幸福呢，那这样还算是浪费金钱吗？
换句话讲，你可能不会有足够的时间去为接下来的一周去购买主食的食材，那么这种情况下准备一个印象深刻的午餐并享受约会可能就是在浪费你的金钱了。
所有的事都是相对的。当我是一个人时，对我可能是一个不错的选择，对于你可能就是最坏的选择。
就拿iPhone举例吧，很多人觉得买iPhone就是浪费钱。对我来说就不这么认为了。在澳大利亚，随着我们人口不断的增多，电话服务费用是极其昂贵的。我父母和爷爷奶奶们每个月在固定电话费用上要花非常多的钱。他们的话费账单已经超过我的iPhone手机的价格，我老婆的iPhone通话和网络连接就已经完全满足了她的需求了，这样我们几乎不用固定电话来通话了。在澳大利亚，移动通信公司提供手机并包含相当多的无限量通话和短信服务。（有这好事？）这样我们的iPhone就比固定电话的花销要少很多了。我们也经常使用手机来娱乐，因此，手机的体现的价值就比基本通话功能就大很多了。所以这也不算是浪费金钱吧。
假如你有两种食物选择，第一种是第二种价格的一半。两种都可以使我吃饱。第一种是很普通的。第二种的花费令我难以想象而且我需要思前想后是否要选这个。假使两种都是巧克力，我会感到很吃惊，一个如此便宜，一个又贵的要死。但是我可以轻松的支付两种。但是我对于便宜的巧克力就很无感。因为第二种是第一种的双倍价格，而第一种常常会让购买的人感到后悔或没有花钱的酸爽，那么第一种便宜的选择就是在浪费钱。相同的理念可以应用到任何事物中，比如电脑，我拥有几台笔记本电脑（因为这是我工作的一部分），但是MacBook Pro可以做的没有其他任何一台可以比得上的，可能会有很多细节的原因，但是一个主要原因是虚荣心，好吧，对于我来说花费在虚荣心上的钱就是值！！（只想对答主说：你赢了）
现在我们试想一下Tim Cook。他想要一个私人空间。它可以选择坐廉价航空的经济舱。但是一个私人空间意味着他将享受网络，移动电话以及想怎么打就怎么打的移动电话服务。虽然这些额外的优势服务远远超出了旅程的花费，这就并不能算是浪费钱。（因为伦家是Tim Cook，而我们是cook）
假如一个人有10亿美元的身价，那它花费5万美元在一场演出上会给人家带来极大的心灵上的满足，那为啥不去花这钱呢。如果花费5w美金让他们感觉真特么便宜然后感觉有点后悔（怎么就这么点钱），那真是一种浪费啊。
好吧，最后答主想说的是，如果你能够从花费中汲取到一丝优势感，那么你就做出了明智的消费。如果你从从话费中感受到并没有什么卵用，那么你就是在浪费钱了。
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汝城里人会玩矣！！