That's a common math fallacy. Let's examine the logic a bit closer.
100 banners at $180 = $18,000.00 setup, printed, and finished.
Material cost of 100 banners = $3,600.00
Average time per banner to setup, produce and finish = 2 hours
Average value of your time = $12.00 to $15.00 per hour
Investment needed for equipment, software and inventory = $20,000.00 to $25,000.00
Expected life of equipment = 5 years
Maintenance cost per year = $1,000.00
Materials = $3,600.00
Labor = $2,400.00
Total time and materials for 100 banners = $6,000.00
Cost per banner for time and materials = $60.00
Equipment per year = $4,000.00
Maintenance per year = $1,000.00
Total equipment cost per year = $5,000.00
Cost per banner at 100 banners per year = $50.00
Savings if volume is 100 banners per year = $7,000.00
Savings if volume is 200 banners per year = $19,000.00
Savings if you shop around for a supplier who is more competitive, say willing for the volume to handle your needs at $3.00 to $4.00 per square foot:
100 banners = $18,000.00 to $36,000.00
200 banners = $36,000.00 to $72,000.00
The numbers speak for themselves.