buysell.software
Software MBA · Lesson 1

What a sale is worth, and where sales come from

No theory. One real product, one real week, every sale counted. By the end you’ll know the two numbers every software business runs on.

AppZapper is our first product: a Mac app that removes other apps and the files they leave behind. It’s the first piece of software on the buysell.software shelf, not the last. Its sales are the only real numbers we have, so every lesson starts there.

1. The receipt

Every AppZapper sale is recorded the moment it’s paid. Here’s the first week, straight from that record:

Day (2026)SalesKeptPer sale
Sep 20from 11am33$758.58$22.99
Sep 21quiet67$1,271.35$18.98
Sep 22quiet32$635.17$19.85
Sep 23Daring Fireball283$5,039.11$17.81
Sep 24the day after138$2,588.88$18.76
Sep 25email to past buyers132$2,252.83$17.07
Sep 26part of the day82$1,414.00$17.24
Week767$13,959.92$18.20

“Kept” means what’s left after the card company takes its fee. That’s the money a business can actually spend.

Number one: a sale of AppZapper is worth $18.20.

Not the price on the page. What’s kept. Every plan (ads, commissions, payouts, “what if we had 10,000 members”) starts by multiplying something by this number. Get it wrong and every plan built on it is wrong too.

2. Quiet days and loud days

Daring Fireball is John Gruber’s Apple blog, read by a lot of Mac people. He wrote about AppZapper on Sep 23. On Sep 25 AppZapper emailed people who had bought it before.

Only two full days had no blog post and no email: Sep 21 (67 sales) and Sep 22 (32). Average them and a normal day is about 50 sales. That’s a guess from just two days, and we say so.

Daring Fireball day: 283 ÷ 50 = 5.7× a normal day
Sep 23 → 25: 283 + 138 + 132 = 553 of the week’s 767 sales (72%)

Number two: sales come from attention, in bursts.

Seven out of ten sales that week came from three days when someone with an audience pointed at the product. The software didn’t change. The attention did.

3. The trade nobody tells you about

Look at the “per sale” column again. On the three loud days each sale kept $17.87 on average. On the two quiet days it kept $19.26.

Why less? Probably a discount: the blog post and the email came with a lower price for their readers. That’s our best guess, not something we’ve checked sale by sale.

Loud days: 553 sales × $17.87 = $9,880.82 kept
Same 3 days at a quiet pace: 3 × 50 × $19.26 = about $2,889
Difference: about $7,000 more, for giving up about $1.39 a sale

A small discount in front of a big audience beat full price in front of nobody. By a lot.

4. What this means if you own a piece

A buysell.software owner’s link is a tiny Daring Fireball. You don’t need Gruber’s audience. You need a few people who trust you and would actually use the thing.

At the split we’re starting with (20% of a sale to whoever’s link sold it, a guess we’ll revisit), one sale through your link pays $3.64. About three a month covers a $10 membership. Everything after that is yours.

Try this before lesson 2

  1. Pick one piece of software you pay for. Any kind: an app, a plugin, a game, a web tool.
  2. Guess what the maker keeps from your payment, not the price.
  3. Guess how many people bought it yesterday.
  4. Think of the last time you told someone about it. That was a sale-sized burst of attention, and nobody paid you for it.

Source: AppZapper’s own sales record, Sep 20–26 2026 (Pacific time). Sep 20 and Sep 26 are part-days. “Normal day” = (67 + 32) ÷ 2 = 49.5, rounded to 50. The 20% link share is a starting guess.