Packing it yourself costs materials plus your hours. A warehouse costs storage plus a fee per order. Drag the orders up and see the month the lines cross.
Self-ship per order = materials + (minutes to pack ÷ 60) × what your hour is worth. At low volume your hours are nearly free, so self-ship wins.
3PL per month = storage and account fees + pick-and-pack × orders. The fixed part is what makes it lose at low volume and win at high volume.
The crossover is storage ÷ (self-ship per order − pick-and-pack per order). Postage is left out because you pay it both ways.
Compare all 4 fees on a quote before you sign: receiving, storage, pick-and-pack, and shipping. A cheap pick-and-pack fee means nothing if storage is brutal.
Not there yet? The Fulfillment Picker. Still shipping from home? The Postage Gap.