Erika Kullberg’s apps

7-Day Purchase Rule / Wish List

Save a desired purchase, wait seven days, then decide whether to buy.

Anything wanted goes on a list and waits seven days. Most things are quietly abandoned; the ones that survive get bought without guilt. The app keeps score of what the waiting has saved.

What a v1 does5 features
  • A wish list with a seven-day timer on every item
  • A prompt when the timer ends: still want this?
  • A running total of what was skipped
  • Price watching, in case the answer becomes yes cheaper
  • A deliberate buy button for the things that survive

The market

Proven marketBudgeting apps
10M membersat Rocket Money, which charges for budgeting and bill management

Monarch has roughly 1.8M monthly users and YNAB about 1.4M, at $99.99 and $109 a year. Mint's closure left the largest gap in consumer finance and three paid products grew into it. This is costed at $4 a month.

Where these numbers come from
CompanyEarnsReachSource
Rocket Money$880M+ saved for members10M+ membersCompany-stated, 2025
Monarch Money$99.99–199 a year~1.8M monthly active usersPublished pricing, 2026
YNAB$109 a year~1.4M monthly active usersPublished pricing, 2026

Why this audience

This is an audience taught by named rules, and the waiting rule is one of the most repeatable. They have heard it and apply it inconsistently. An app that enforces the wait and counts what it saved makes the rule real.

Before it can launch

No licence, certification or data agreement stands between this and a launch — app-store review and an ordinary privacy policy aside.

How the pricing works

Four dollars to be talked out of buying things. It renews because the counter of what was skipped is visible - the app has to show its own saving or the renewal has no argument.

What it earns

Drag me Every figure recalculates as you go.

Paying users1,000

0.0047% of 21.2M followers · capped at 50,000

Price per month$4

Opens on the price this idea was costed at, $4.

1,000 paying — 0.0047% of 21.2M followers — × $4 a month = $4,000 a month

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Revenue a month$0123456789,012345678901234567890123456789
Over twelve months$01234567890123456789,012345678901234567890123456789

Fifty thousand paying users is the ceiling every one of these pages is drawn against, not a forecast. It opens at a thousand, the bottom of the range, so the first figures you see are the modest ones. What the cap buys is comparability: the same range on every app, and the percentage of the audience it takes as the number that moves.

Is this the one for your audience?

We fund it, build it, and run it. You bring the audience and take a share of the revenue. Nothing to pay and nothing to build.

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