Units times price is the gross
The top line is straightforward: 300 units of a $49 product is $14,700 of gross sales for the month. Digital means that gross has no cost of goods behind it - the same file serves one buyer or a thousand - which is genuinely powerful and also the reason the rest of the page matters so much.
Gross is only the conversation starter. The page keeps working downward because platform fees and traffic costs both come off the top, and a product with an impressive gross can still hand back very little. The table prints price, units, gross, fee, fee amount, ad spend, net and net per unit in that order so the descent is visible.
With no units entered the gross is zero and the month becomes the ad spend as a loss, which the page reports without special-casing it. There is no minimum volume to reach before the arithmetic applies.
Platform fees and ad spend come off
The marketplace or payment processor takes a percentage of each sale, and that percentage is charged on the gross rather than on the profit. If you are also paying for the traffic that produced the sales, that spend is a real cost of the same month, subtracted after the fee because the fee is charged per transaction while the ads are a monthly bill.
The danger the page is built to expose is a funnel where ad spend outruns the margin left after fees. On $5,800 of gross, a 12 percent platform fee leaves $5,104, and $5,000 of ads brings the month down to about $104 - a result the page reports plainly instead of calling it a growth story.
The yearly figure is the monthly net multiplied by twelve, offered because one month is a noisy way to judge a product. It inherits the month assumptions exactly, so a bad month extrapolates into a bad year rather than averaging itself out.
Net per unit is the real margin
Gross less the platform fee, divided by the units, is what each sale brings in before traffic is paid for - about $43 on the default case. That is the number to hold against what it costs you to acquire a buyer, because a product only scales when the margin on a sale exceeds the price of finding the next customer.
The page keeps ad spend on its own line rather than folding it into the per-unit figure, so the comparison stays clean. Ad spend is a monthly total; spreading a fixed bill across however many sales happened to occur would flatter a good month and punish a bad one for the same campaign.
Read the per-unit figure first, then the monthly net. A healthy per-unit margin with a negative net says the traffic bill is the problem; a thin per-unit margin says no amount of traffic will fix it.
Price is a lever, not just a sticker
A higher price on the same units multiplies the net, because there is no unit cost adding on top to absorb it. A $49 product sold to 300 buyers grosses more than a $19 product sold to twice as many, and the page makes that trade visible in plain dollars rather than in percentages of an unknown base.
The constraint is conversion, and it is not on the page because it is not arithmetic. A price only earns if buyers still move at it, so the honest use of the calculator is to change the price, read the net, and then check the sales figure against what the store actually sold at that price.
Refunds, currency conversion and platform minimum monthly fees are not modeled, and the sources say so. What the page does answer is narrow and exact: at the price, volume and fee you entered, how much does the product leave behind each month.
The break-even unit count, and why ads are a fixed cost
Ad spend is the only fixed cost on this page. The platform fee scales with every sale, so on its own it can never put the product underwater; the ad budget can, because it is spent whether the units arrive or not. Divide the spend by what one unit keeps after the fee and you get the break-even count: $2,000 over $43.12 is about 46 downloads a month. Under that number the product loses money no matter how good the price looks on the page.
Above it, every extra unit is worth the same $43.12 rather than the $49 on the price tag, and that marginal number is what a discount has to be measured against. Ten percent off takes $4.90 off the sticker but only $4.31 off the margin, so the break-even count climbs from about 46 to 51. A ten percent price rise does the opposite: break-even falls to 42 and every sale you already had becomes worth $4.90 more, with no extra traffic bought.
That asymmetry is the whole argument for selling to people who already want the thing. Buying more traffic at the same conversion rate only pays when the price already covers the fixed spend with room to spare, which is exactly what the net-per-unit line is telling you. If that line is thin, more ads make the loss bigger, not smaller.
Danfio