The psychologist Dan Ariely tells a story about an eye-opening encounter – as opposed to the more normal door-opening kind – with a locksmith. Business was bad, the locksmith confided. When he was starting out, picking locks took him for ever, and sometimes he'd have to smash them open, but customers appreciated his efforts and gave generous tips. Now, as a veteran, lock-picking took him mere moments, and his clients, seeing how easy he found it, had stopped tipping. Worse, they even resented paying his fees for what seemed like so little elbow-grease. Perhaps the locksmith should have heeded the timeworn tale of the industrialist whose production line inexplicably breaks down, costing him millions per day. He finally tracks down an expert who takes out a screwdriver, turns one screw, and then – as the factory cranks back to life – presents a bill for £10,000. Affronted, the factory owner demands an itemised version. The expert is happy to oblige: "For turning a screw: £1. For knowing which screw to turn: £9,999."

Both stories illustrate a hidden agenda that bedevils how we think about paying for services: we imagine all we want is a specific result, yet as often as not we're equally interested in seeing that someone breaks a sweat on our behalf. This so-called "labour illusion" works even when that someone is a computer, which is why travel-booking sites like Kayak.com make such ostentatious display of searching airline after airline for flights. In one recent experiment, by the Harvard Business School researchers Ryan Buell and Michael Norton, people using a flight-search site actually preferred waiting 60 seconds over getting instant results, provided they got to look at what appeared to be a running tally of the tasks being executed. This may also be why some voice-recognition customer service lines use prerecorded "typing" sound effects, to make it seem as if your details are being laboriously entered. Sadly, the notion that cashpoints use a similarly fake "whirring" sound when dispensing money appears to be a myth – but a pleasing one that, consequently, I intend to help promulgate.

To Buell and Norton, this is an argument for "transparency" – for businesses letting customers see their inner workings. But it's as easy to see it as an argument for a certain dishonesty. If you want to charge more for your services as a plumber or web designer, consider pretending you need more time than you do, then issue regular updates, genuine or otherwise, on the effort you're expending. It's also an argument for staying aware of when we might fall for the illusion ourselves. If you're a manager, do you reward "hard workers" and those who "give their all" with promotions and pay rises? That's often how it works. But it's not obvious why how much of themselves someone gives – as opposed to what they deliver – is any of your business.

There are times, of course, where the labour illusion is no illusion. When a child gives you a handmade present, the effort constitutes much of the value. (Note to self: that must be why they burst into tears when I point out the gifts are rubbish!) But it's alarming to consider that we might unconsciously apply the same mindset in contexts such as commerce. You're locked out of your house. You want to get back in. This isn't the time to be imposing your beliefs about the virtues of hard work on the locksmith.

• oliver.burkeman@theguardian.com; twitter.com/oliverburkeman