Packaging has two layers: visual communication and physical production. A design can look excellent and still be unusable if it ignores the approved dieline, glue areas, substrate or printer requirements.
What the brief should include
Supply product/SKU, target customer, sales channel, logo and brand rules, approved copy and legal markings, barcode, languages, confirmed dieline and known production specification.
Who owns the dieline
The packaging manufacturer or structural packaging specialist should provide or approve the dieline for the actual material and production method. A graphic designer should not reverse-engineer construction from a competitor photo.
What changes the design cost
Format complexity, number of panels and SKUs, illustration, retouching, 3D mockups, language versions and how complete the supplied data is all change the workload.
Mockup versus production artwork
A 3D mockup helps approve direction. The final artwork must still sit on the correct production template with bleed, safe zones, colours, images, fonts and finishing layers checked.
Build a master before variants
For several flavours, sizes or countries, lock shared elements in one master and define exactly which fields may change. This reduces accidental drift between SKUs.