Priced per unit with quantity breaks. Vendors quote steps at 1 / 5 / 10 / 25 / 50 / 100 units, and the per-unit rate drops at each break.
No. Commercial-grade hardware is reusable for years. Buy the frame once and reorder only the printed graphic, which is the cheaper part.
Mechanism grade. An economy unit and a commercial one look alike on paper but the cheap one fails sooner. Pin the hardware grade before comparing.
The same product family is tracked in 11×17, 8.5×11. Quotes are NOT interchangeable across variants, so match the spec before comparing.