What the numbers say
Buy two at $200.00, get a pair of socks free: a different product, one the store also sells, at $15.00. Against a buyer of two who takes nothing more, the free product costs $9.33 per order: its unit cost and one more pick.
Against a buyer who would have added it at full price, the offer gives up $11.67: the $15.00 they would have paid, less the card fee and the refund reserve on it. That order kept $28.66; with the product free it keeps $16.99.
To earn what selling two earns per visitor, it needs 54.9% more buyers. The offer pays when it moves one-unit buyers up to two, and costs most where buyers were already paying for the free product: choose one that few orders hold.
The cost structure, and where it comes from
| Price | $100.00, a pair of sneakers. Allbirds, Men's Tree Runner, read 13 October 2026 |
|---|---|
| Unit cost | $59.00. From the income statement: revenue $152.5 million, gross profit $62.6 million, a gross margin of 41.0%. Allbirds (Smartbird, Inc.), annual report (Form 10-K) for the year ended 2025-12-31, read 13 October 2026 |
| Pick and pack | $3.20 per order and $0.48 for each extra item. Fulfill.com, 3PL pricing benchmarks (The Fulfillment Advisor 2025 survey of 600+ warehouses), read 23 September 2026 |
| Shipping label | USPS Ground Advantage, commercial, Zone 5, by weight rounded up to the pound: 1 lb $9.29 · 2 lb $10.50 · 3 lb $12.12 · 4 lb $13.89 · 5 lb $14.53. Packed weight is an assumption: 2.5 lb per unit. USPS Notice 123, USPS Ground Advantage Commercial, Zone 5 (effective 4 October 2026), read 13 October 2026 |
| Card fees | 2.9% + $0.30 per order: Shopify Payments' online rate for a standard card on the Basic plan in the United States. Higher plans pay a lower rate, and premium cards a higher one. Shopify's pricing page for the United States, online standard card rates, read 12 October 2026 Rates by plan and country |
| Refund reserve | 19.3%, NRF's estimate of online sales returned in 2025, across all categories. NRF and Happy Returns, 2025 Retail Returns Landscape (15 October 2025), read 23 September 2026 |
| Gift | A pair of socks: unit cost $8.85, retail $15.00. A $15 pair of socks, costed at Allbirds' reported gross margin. |
The offer, as an agent writes it
An agent writes this offer as one document for Offer Suite's API, validated against the offer schema. Below is one option of it: what the buyer gets and the price it promises. Offer Suite checks with a real cart that checkout charges exactly the prices above.
Show one option 2 options · excerpt
{
"key": "two-get-one-free",
"display": {
"title": "Buy 2, get a pair of socks free"
},
"lines": [
{
"role": "main",
"quantity": 2,
"purchase": {
"type": "one_time"
}
},
{
"role": "gift",
"quantity": 1,
"purchase": {
"type": "one_time"
}
}
],
"pricing": {
"promise": {
"firstChargeCents": 20000,
"renewalChargeCents": null
}
}
}How Offer Suite validates, versions and publishes a document like this one: offer documents.
Questions
Is buy two, get another product free profitable for footwear brands?
On these costs, with a pair of socks as the free product, the order keeps $16.99, $9.33 less than two units alone. It is profitable while it brings buyers of two who would not have come.
Which product should footwear brands give away?
One that costs little to make and that few buyers already pay for. Here it has a unit cost of $8.85 against a price of $15.00: free, it costs $9.33 on an order that would not have held it and $11.67 on one that would have paid for it.