If you sell 3D prints, what's currently the most frustrating part of it?

I’m researching common challenges 3D-print sellers face. If your answer isn’t listed, please leave a comment. I’d love to hear what’s causing the most headaches for makers and sellers.

Options

Pricing products correctly

Creating listings and descriptions

Tracking filament/material costs

Shipping and packaging

Finding products that actually sell

Managing inventory

Marketplace fees (Etsy, eBay, etc.)

Managing orders and customers

Calculating profits accurately

Other (Please comment)