28x20 inches
Priced per unit; vendors typically quote against a primary quantity around 1 unit.
Usually substrate or finishing, not the printing itself. Ask both vendors to quote the identical substrate and finish and the gap normally closes.
Yes for short runs, but it should be charged once per design, not per unit and not again on a reorder of the same file.
Related variants of this product are tracked as separate benchmark lines. Match the spec before comparing quotes.