Because you're pulling data from a dozen different sources and none of them talk to each other.
Inventory.
You need to know exactly what's on hand — not just in FBA, but in AWD, at your 3PL, and at your supplier's warehouse in China. For FBA alone, that's a separate inventory report downloaded from Seller Central for every single country. US, Canada, UK, Germany, France, Italy, Spain, Japan — each one a separate download, a separate file. AWD? Separate Excel exports. 3PL warehouses? Often there's no system at all — just receipts, invoices, and your own spreadsheets. You store large batches at a 3PL because it's cheaper than Amazon's warehouses, then drip-feed smaller shipments to FBA as stock runs low. Every move in and out — you're tracking it manually. When you have 16 marketplaces, just collecting this data is days of work.
Shipments in transit.
What's already on the water? What's cleared customs but hasn't been checked in yet? What's sitting in "receiving" at Amazon — which can be 15% of your FBA stock at any given time? You need to account for all of it. Miss a shipment and you'll over-order, tying up cash and racking up storage fees. Forget one and you'll go OOS during Prime Day — the worst possible time.
Sales velocity.
Amazon doesn't give you a velocity report. You take units sold, divide by days, and do it per product, per marketplace. And there are quirks you need to remember for each market. A sale in Italy might ship from a German warehouse — so is that German velocity or Italian? It matters, because your restock math depends on getting this right.
Demand forecast.
You can't just project current velocity forward — Prime Day changes everything. Here's what this seller's forecast looked like:
Per product. Per marketplace. Dozens of calculations, each one requiring historical data you have to dig up manually.
- Days 1–45(current period): average velocity from Feb–March
- Days 46–90(pre-Prime season): year-over-year coefficient from the same period last year
- Days 91–137(Prime Day window): last year's Prime Day multiplier
Gap analysis.
Compare projected demand against available stock — on hand plus in transit plus on order. Identify shortfalls. For each shortfall: how many units to order, from which supplier, how many boxes you need. And the boxes come from a separate supplier — do they even have enough in stock? If not, you need to place a rush order for more boxes before you can even start packing.
Shipment planning.
Calculate CBM and weight per product, figure out what fits in a container and what goes LCL, price out freight, allocate across destinations. And you have to get the consolidation right — customs paperwork costs ~$200 per document whether you're shipping 5 units or 300,000. Send a small batch separately because the timing didn't line up? You just blew up your unit economics. So you need to know exactly when each supplier will have product ready, coordinate pickups, and combine everything into a single customs declaration per destination.
And at every step — double-checking.
In a process this fragmented, mistakes are everywhere. A wrong velocity number cascades through your entire plan. A missed shipment means you're reordering stock that's already on the water. One bad formula in your Excel blows up three tabs downstream.
All of this in spreadsheets. All manual. Minimum 10 working days. And the person doing it? A supply chain manager based in China — someone who can negotiate with local suppliers in their language, get favorable production slots, coordinate consolidation on the ground, AND do all the analytical work in Excel, AND communicate with you in English. That combination of skills doesn't come cheap. $3,000/month minimum.
