A quantity discount is not the same decision as combined
shipping, a seller-initiated offer, or Promoted Offsite.
Combined shipping is already-sold different items and no
price cut. An offer to watchers is one unit. Offsite is a
campaign billed even if they bounce. Here you cut the item
price so one buyer takes N of the same SKU.
The listing and the discount
Discount vs singles
$—
extra kept by the discount versus singles
Singles after sell-through
Discount after take rate
If they buy two singles
If they take the multi-buy
Take rate that still ties singles
Discount-percent ceiling on leftover
Packed leftover gap
Monthly gap vs singles
Same SKU, two ways to move two units
Path
Shipments
Unit price
Close rate
If they keep it
Expected after sell-through
vs singles
Postage, the discount, and both close rates are inputs — not eBay’s volume-pricing policy.
What this checks
Card, clothing, and small-goods sellers search “should I
offer an eBay quantity discount” because listing settings
show Buy 2, get 10% off as a default first tier. A volume
coupon looks like free sell-through. It also writes a new
ticket on every unit in the box, and a 20% “make them take
two” discount can leave less than two singles at list.
On the defaults — $40 item, $6 shipping charged, 13.6%
final value fee, $0.40 fixed, $12 cost, $5 outbound, $1 pack,
$5 return label, 10% returns, two units, 10% off, $6 charged
/ $5.50 postage / $1.25 pack on the multi-buy, 55% singles
sell-through, 70% take rate, twenty orders — two singles
expect $19.92 and the discount expects $21.97. The discount
keeps $2.05 more on this decision and +$41.09 across twenty
orders. The multi-buy has to be taken about 63.5% of the
time, or stay at or below about 2.2% off, before it matches
selling separately. If they would have bought two anyway,
leftover shrinks $4.83 ($36.22 vs $31.39).
A deeper coupon flips. Keep the same listing and offer 20%
off two. Singles still expect $19.92; the 20% discount
expects $17.62 — $2.30 less. Matching the 55% singles
sell-through already loses on a 10% discount ($17.27 vs
$19.92). The conversion you thought you bought did not cover
the leftover you gave away.
A quantity discount is a pricing decision on a multi-quantity listing. You either sell N units as separate singles at the listed price or cut the item price so one buyer takes all N, pays shipping once, and gets one box. On the calculator defaults ($40 item, $6 shipping charged, 13.6% final value fee, $12 cost, $5 outbound, $1 pack, 10% returns, two units, 10% off, $6 / $5.50 / $1.25 one box, 55% singles sell-through, 70% take rate) two singles expect $19.92 and the discount expects $21.97. The discount keeps $2.05 more after sell-through. On leftover — if they would have bought two anyway — two singles leave $36.22 and the discount leaves $31.39, $4.83 less. The multi-buy has to be taken about 63.5% of the time, or stay at or below about 2.2% off, before it matches selling separately. That is arithmetic on your inputs, not advice to turn the discount on.
When does selling separately beat an eBay quantity discount?
When the discount eats more leftover than the take-rate lift returns. On the same $40 listing, a 20% off-two coupon at a 70% take rate expects $17.62 against $19.92 for two singles — $2.30 less. Matching the 55% singles sell-through already loses on a 10% discount ($17.27 vs $19.92).
Is a quantity discount the same as combined shipping or an offer to watchers?
No. Combined shipping is already-sold different items and no price cut. A seller-initiated offer is one unit, percent off to watchers. Lot versus singles is one listing of a pile versus N listings. Promoted Offsite is a campaign billed even if they bounce. A quantity discount cuts the item price on the same SKU so one checkout takes N units.