Could the Market Pay Your Grocery Bill?

Every month you spend $600 on food, you also invest $600. Whatever you eat, you match. The $600 sits in a diversified portfolio for six months. Under an illustrative 10% annual return assumption, that batch grows by about $30 in that window. After six months, you take the $30. The $600 stays. In a down stretch there is no $30 to take, and the $600 itself can be worth less than you put in.²

Illustrative only: 10% assumed annual return, the S&P 500's long-run average since 1957. Not a forecast or a guarantee. Real results will differ and you can lose money.

That last sentence is the whole thing.

The $600 stays.

When most people hear “investing,” they picture a one-time deposit that compounds on its own. That is the idea, but at the scale of a normal life it moves slowly. The part worth looking at is what happens when a single $600 stays invested while you keep adding new $600s alongside it. In this model the first batch is never sold off. It gets pruned. The fruit comes off, the tree stays, and it can fruit again if the market cooperates.

Now follow what that does over time.

You make your first deposit in January. The market does what markets do, which is shake around and roughly drift up. By July, that first $600 has grown to about $630. You take the $30. The $600 goes back in for another six months.

In August, your second deposit (the one from February) matures. Another $30. Then September. October. November. December. Through the rest of the year, $30 a month trickles in.

It’s nothing. A coffee. A side of fries. You almost don’t notice.

This is the part that loses most people. The first year doesn’t feel like progress. By December, you’ve recovered $184 against the $7,200 you matched. A 2.6% rebate. Your grocery store loyalty card does better than that.

But the river is filling.

In January of year two, the very first deposit you ever made comes due again. Same $600. Same gain. The fruit grew back.

But you also have a new batch maturing for the first time, the one you put in seven months ago. So January doesn’t give you $30. It gives you $60.

February: $60. March: $60.

Then July arrives. Batch one is on its third harvest. Batch seven is on its second. The batch from January of year two is hitting its first. That’s three checks in one month. $90.

By December of year two, you’re collecting three batches a month. $90 against a $600 bill. Still small. But you can feel something building underneath.

Here’s what people miss the first time they hear this. You didn’t add anything new to make it accelerate. You just kept doing what you were doing. The acceleration came from the principal staying put. In the model, each batch keeps paying out twice a year for as long as it is held and the return holds up. You’ve been quietly building a portfolio of small annuities, six months at a time, without thinking of it that way.

Every six months, one more batch joins the steady harvest. Every year, two more.

Year three: by December, you’re collecting $150 a month. A quarter of the food bill, returned.

Year five: $270 a month. Almost half.

Year seven: $390 a month. Two thirds.

Year nine: $510 a month. You can almost taste it.

None of these are separate streams. It’s the same $600 you put in years ago, still working, still paying. Multiplied by every other $600 you put in alongside it. Each one a small annuity. None of them ever leaving.

This is where the chain breaks for most people. The numbers feel small relative to the time it’s taking. You compare them to what you could have done with the money. You move on to a different idea. The chain breaks. The clock resets.

But if you don’t break it, year ten happens.

Ten years in. Twenty batches mature in the same month. Twenty checks of $30 each.

$600.

That’s the size of the food bill.

You walk into a grocery store. You fill the cart. Under the assumptions in this illustration, the receipt could be covered by gains on principal you parked years ago. Whether it actually is depends on what the market did over those ten years.

It happens quietly. There’s no celebration, no notification, no banner across the top of an app. The math finally catches up. From this month forward, every batch you’ve ever put in keeps doing what it was already doing. Every six months, the same money pays you again. The harvest doesn’t care whether you’re paying attention.

In the model, year eleven is where the gains exceed the food bill and a little is left over.

Year twelve, a little more.

By year fifteen the model has food spending running as a small net positive. Everything past this point is the assumed return continuing to hold, which is exactly the part nobody can promise.

You did not win the lottery. You did not get lucky. You did one thing every month for ten years and refused to let the principal go.

This is not a hack. Not a budget trick. Not gymnastics. It’s the most ordinary fact about money applied to the most ordinary fact about life.

Money you don’t need today is supposed to work. Idle cash is a strange thing if you stop and look at it. It’s the only asset class that gets worse the longer you hold it. Inflation eats it. Time eats it. Doing nothing with money is paying someone to slowly take it from you.

Equity does the opposite. A share of a productive business is just stored labor that produces more labor while it sits. Fischer Black wrote about this fifty years ago, and it’s still the cleanest way to think about it. A share of a real company and a dollar in your checking account are not different in kind. One of them is paying you to hold it. The other isn’t.

What I’ve described is what wealthy families have always done with food. They don’t think of food as a cost. They think of it as something the dividends cover. It was never the price of food that made eating feel expensive. It was the assumption that every dollar of food spending had to come from a paycheck.

It doesn’t.

This is what we built Coinage to do. Connect your brokerage. Connect the card you actually use. Pick a portfolio. Match what you spend. The gains, every six months, get applied to the bills you would have paid anyway. The principal stays where it is, kept clean and growing, season after season. You keep eating, going out, traveling, living. The portfolio runs underneath all of it.

Food is the cleanest expense to model, but the same arithmetic applies to gas, rent, subscriptions, the gym, the streaming services, the things you barely register paying for. Anything you spend on, you can match. What the match earns is up to the market.

The hard part is that nobody can do it for you. The chain has to stay unbroken. Principal stays. Gains harvest. Bills get paid by the harvest. The first year feels like nothing. The fifth year feels like progress. The tenth year feels like sorcery.

But it’s not sorcery. It’s just what money is supposed to do, finally allowed to do it.

Eventually, if the assumptions hold, the food could be paid for by the harvest.

And if they don’t, it isn’t. That is the honest shape of it.