Everyone knows money can't buy happiness. But you can occasionally pony up for a little temporary bliss. Like a tropical cruise. Or a fancy drink with an umbrella in it.

Or a new mattress.

Wait — what? Of all the potentially joy-inducing things you could buy, how does a mattress find its way into the same train of thought as tropical cruise?

What if we told you that with a new bed you could embark on a fabulous free vacation every single night? Maybe it's Casablanca. In the 1930s. Or maybe you're at the helm of your own yacht on a tropical planet — named after you, of course.

You'd probably tell us replacing vacations with dreams of vacations is pretty cheap.

But even if you don't subscribe to the dreams-as-vacation theory — or perhaps you're prone to nightmares — you can't deny sleep's crucial role in maintaining your health, and by extension, your happiness.

And in that sense, you might be surprised to learn how well a sturdy mattress stacks up against a vacation cruise.

In fact, a mattress may be the most cost-effective way to find happiness.

Consider the simple formula Eric Ravenscraft, writing for The New York Times, came up with when he compared the happiness-per-dollar value of a comfy chair to a video game:

"I've spent at least eight hours a day, five days a week in the chair (I work from home.) Over a mere three months, that would add up to 480 hours in the chair. Since the chair costs $160, I've paid a paltry $0.33 per hour of sitting. After a year, that would be down to about $0.08 per hour. In order to get that same cost-effectiveness from Super Mario Party, I would have to play it for over 750 hours. The game's fun, but not that fun."

Eight cents an hour for a measure of happiness is a good deal. And that's just a chair. If we really put our "fun" money into the areas of our lives where we spend the most time, then consider the greatest, most abiding human pastime of all: sleep.

Nothing occupies more of our time than sleep — at least, ideally, nothing should. It's a full third of our lives.

Do the math

Woman looking out at sea from a cruise ship. You can find happiness on a cruise. But at what cost? (Photo: Igor_Koptilin/Shutterstock)

A vacation cruise, if you're lucky, lasts seven days, and maybe costs $2,000. Let's also assume that you spend every moment of those seven days in a state of comfort. No long lines to embark and disembark from the ship. No gastrointestinal distress from the dubious shrimp at the buffet table. No hangovers.

That would be 168 hours of happiness for $2,000. Under the Ravenscraft rule, that clocks in at just under 20 cents per minute.

Now, let's apply the same formula to a bed. Not just any bed — let's treat ourselves to a model from the Royal Sovereign Victory Collection from luxury mattress maven Kluft, which retails for around $5,000.

Assume you sleep for eight hours per night — and, as with the cruise, every minute of that sleep is a good experience. No nightmares. No bedbugs!

That's 2,920 hours a year we'd spend on a cloud called Kluft. Or 175,200 minutes.

At what cost? A measly three cents per minute.

Now, if that mattress should last 10 years, that's 0.3 cents per minute.

Compare that to the princely 20 cents per minute you're forking over for a tropical excursion.

But, you may groan, it's somewhere else. And, as Jimmy Buffet reminds us, "nibblin' on sponge cake, watchin' the sun bake" may be a worth paying a premium for.

Just keep one more thing in mind: The "happiness value" of that cruise may also decline over time. There's plenty of research to suggest buying things, like vacations and gadgets and margaritas may make us happy for a little while. But the amount of happiness we get from them declines over time. When was the last time you got bored of sleeping?

Or, at least, bored of getting a good night's rest and feeling powerfully refreshed the next day?

A good bed may seem like a boring thing to buy. But it's your best bet for squeezing more happiness out of your days over the long term.

The math of happiness — or why a new bed is better than 7-day cruise
There's no better way to spend your dollars than on a good bed. It even beats a nice vacation.