Why use 7% as the investment return?

It approximates the long-run nominal return of a globally diversified equity portfolio, and it is the most common planning assumption. Using 5% instead reduces the ten-year multiple from about 173x to about 155x — the conclusion rarely changes, only the magnitude.

Isn't opportunity cost just an argument against spending on anything?

Every purchase has an opportunity cost, so the concept only becomes useful when comparing similar amounts. Its power with subscriptions is that many of them deliver no value at all, which makes the trade-off one-sided rather than a genuine choice between two goods.

How do I account for annual price increases?

Multiply the current price by 1.05 for each future year, or simply add 25-30% to a flat ten-year estimate as an approximation. Most services have raised prices faster than general inflation over the past decade.

Should I cancel a subscription I use often just to invest more?

No. Judge each service on cost per use. Something used twenty times a month at $11 costs $0.44 per use and is excellent value; the leverage is in the services with a high cost per use or none at all.

The 10-Year Opportunity Cost of Recurring Services

Opportunity cost is the value of the best alternative you gave up. For subscriptions, that alternative is almost always the same: the identical amount invested in a diversified portfolio, compounding quietly in the background.

This guide shows how to calculate the true multi-year cost of any recurring charge, including price escalation, and how to use that figure to make keep-or-cancel decisions without moralising about coffee.

The Calculation, Step by Step

A recurring payment invested instead of spent is an annuity, so the future value formula applies directly:

FV = PMT × [((1 + r)ⁿ − 1) ÷ r]

Worked example: one $15 subscription over ten years at 7%

Monthly rate r = 0.07 ÷ 12 = 0.0058333
Periods n = 120
(1.0058333)¹²⁰ = 2.00966
Annuity factor = (2.00966 − 1) ÷ 0.0058333 = 173.08
FV = $15 × 173.08 = $2,596

You paid $1,800 in cash. The opportunity cost is $2,596 — the $1,800 plus $796 of growth you never received.

The full grid

Monthly amount	5 years	10 years	20 years	30 years
$10	$716	$1,731	$5,204	$12,199
$15	$1,074	$2,596	$7,806	$18,298
$25	$1,790	$4,327	$13,010	$30,497
$50	$3,580	$8,654	$26,020	$60,994
$100	$7,159	$17,308	$52,040	$121,987
$200	$14,318	$34,617	$104,081	$243,975

The quick mental shortcut: at 7% over ten years, a monthly subscription costs roughly 173 times its monthly price in foregone portfolio value. A $12 service is about $2,080. A $60 gym is about $10,400.

Adding Price Escalation: The Cost Most Models Miss

Subscriptions do not hold their price. Streaming services, software licences, and gyms have raised prices repeatedly, often by 5-10% annually or in step changes after an introductory period.

Starting price	Flat for 10 yrs (paid)	With 5%/yr increases (paid)	With 8%/yr increases (paid)
$10/mo	$1,200	$1,509	$1,738
$15/mo	$1,800	$2,264	$2,607
$25/mo	$3,000	$3,773	$4,345
$50/mo	$6,000	$7,547	$8,690

At 5% annual increases, a $15 service costs $24.43 a month by year ten and $2,264 in total cash — 26% more than the flat-price estimate. The opportunity cost rises correspondingly, to roughly $3,100 over the decade.

Escalation is a reason to re-decide, not to despair

Every price increase notice is a natural decision point. Providers rely on you treating it as information rather than a question. Two responses are usually available and rarely taken: downgrade to a lower tier, or cancel and use a competitor's introductory offer.

Set a price ceiling per service at signup. Write down the maximum you would pay. When an increase crosses it, cancel without re-litigating the decision — the ceiling was set when you were thinking clearly.

A Framework for Keep-or-Cancel Decisions

Opportunity cost is not an argument for cancelling everything. It is an argument for paying deliberately. Use a cost-per-use figure alongside the ten-year number.

Cost per use

Divide the monthly price by the number of times you actually use the service in a month.

Service	Monthly	Uses/month	Cost per use	10-yr opportunity cost	Verdict
Video service A	$18	16	$1.13	$3,116	Keep
Video service B	$14	2	$7.00	$2,423	Rotate or cancel
Music	$11	25	$0.44	$1,904	Keep
Gym	$55	3	$18.33	$9,519	Cancel or switch to pay-per-visit
Fitness app	$13	0	—	$2,250	Cancel immediately
Cloud storage	$10	Continuous	—	$1,731	Keep, check for duplication
News	$16	8	$2.00	$2,769	Judgement call
Totals	$137	—	—	$23,712	—

In this portfolio, cancelling the gym, the fitness app, and one video service recovers $82 a month — worth about $14,190 over ten years and $42,650 over twenty, with no reduction in anything the household actually used.

Three questions per service: Did I use it in the last 30 days? Is the cost per use below what I would happily pay in cash each time? Would I sign up again today at the current price? Two "no" answers means cancel.

Capturing the Savings So They Actually Compound

This is the step that decides whether the analysis was worth doing. Money saved and not redirected is simply money spent on something else within about six weeks.

Total the cancelled amount to the dollar — say $82 a month.
Increase an existing automated investment transfer by exactly that amount, on the same day you cancel. Do not wait for the next budget review.
Schedule it for payday +1 so it leaves before discretionary spending.
Name the account after the source — "recovered subscriptions" — because a labelled balance is far more resistant to raiding.
Recheck in six months and repeat, adding any new recovery to the same transfer.

What this looks like over a career

Recovered monthly	10 years	20 years	30 years
$82	$14,193	$42,673	$100,030
$120	$20,770	$62,449	$146,384
$180	$31,154	$93,673	$219,577

A single afternoon of cancellations, redirected and left alone, is worth six figures over a working life. Very few financial decisions offer that ratio of effort to outcome.

Do not moralise the analysis. The point is not that entertainment is wasteful — it is that unused services are pure loss, and the money they consume has an alternative use with a measurable value.

Enter your own list in the subscription cost tracker to see the annual and ten-year figures for your specific portfolio, then use the compound interest calculator to project the recovered amount over your actual horizon.