There's no doubt that children have a very different perception of value from adults - as anyone whose toddler has had a meltdown over a bit of supermarket tat can tell you. And that perception of value carries on evolving throughout our lives.
Three influences on what we buy
In a study carried out in 2007, French researchers looked at the impact of age on the perceived importance of three factors known to influence people when buying clothes: price, durability and suitability.
"For younger participants, a low price was considered a sufficient reason to buy the item of clothing. For older participants, suitability was a more important factor, while for the eldest people, durability was the most important," they write.
"This could be because of the pressure of work, retirement and family obligations felt by people of these age groups that their greatest concern was the money spent and the quality of the goods."
This trend is clearly seen in the rise of online clothes-selling and swap sites such as Depop or Shpock. Hugely popular amongst teenagers, they provide a way of getting something new every week at a very low price. The clothes may or may not be durable, but the people buying them don't really care: the chances are, they'll have swapped them on within a month.
Habits and experience
Older people have also been shown to prefer buying brands that have been established for a long time. When buying a car, one survey revealed, they consider fewer brands, fewer dealers, and fewer models, and pick long-established brands more often. They also repurchase a brand more frequently when they buy a new car.
There are likely to be a number of reasons for this. First, and most obviously, older people really do have more experience - the chances are that they're repurchasing the same brand of car after decades of shopping around. Habit is likely to come into play here too.
The important of being emotional
And another big difference between older and younger people is that the oldies tend to place much more importance on emotionally meaningful goals.
In a 2015 study, young people were found to be motivated most by excitement; the middle-aged by power and success; and older people more by tradition and religiosity. All this comes into play when we consider how much we think something is worth.
In one study, for example, researchers found that people of all ages show a strong preference for cars dating from their youth.
In fact, sentimental value is something that affects us from a very early age. By the age of six, children experience something known as the endowment effect: they value an object more, simply because they own it.
And this feeling can become very strong in old age. In 2000, the University of Arizona's Linda Price interviewed 80 older people about the special possessions they'd had for a long time, and found that most valued some of these items very highly indeed.
"I can look at anything [in this house] and remember special occasions. It’s almost like a history of our life," said one.
In another similar study, carried out in New Zealand, one woman living in a care home explained that a ceramic plate reminded her of her mother, adding: "I love having this plate to keep me company."
Taken to its extreme, of course, this attitude can lead to hoarding - a whole different topic. But several studies have revealed that having possessions that you value for emotional reasons increases overall life satisfaction scores.
"Older people, who perceive their time horizon as limited, place greater emphasis on emotionally meaningful goals - goals related to feelings, such as balancing emotional states - than on knowledge-related goals," writes Yashu Bansal, of the Chanakya National Law University in Patna.
"No matter how many ice cream brands, sundaes and products come up, an old man will stick to eating a ‘koolfi’ if that pleases his taste and mind."
It's fair to say, then, that value, like beauty, is in the eye of the beholder: an object's worth a lot if it's worth a lot to you.