Line 1: "55-inch 3.5 mm panel, qty 9"
Panel grade is the first hidden variable. A, A-minus and unspecified all get called 3.5 mm.A-minus can carry a few bright sub-pixels or a slight brightness variation. In one display nobody notices. In nine panels on a uniform background, one brighter corner is obvious.
Ask for the grade and the pixel acceptance standard in writing. If the answer is 'industrial grade', that is not a grade.
Line 2: "bracket set"
A fixed stamped-steel bracket and a pop-out bracket with machined hinges are different products with different service economics.Check the steel thickness and whether the bracket is adjustable on two axes. A bracket that cannot be adjusted after hanging means every alignment error is corrected by moving the wall.
Line 3: "installation"
One quote includes mounting, alignment and colour calibration. Another delivers boxes to the kerb.On a twelve-panel wall, installation and calibration run 15 to 20 percent of the total. A quote that looks cheap often just ends at the loading dock.
Line 4: "power supply and driver board"
Branded versus unbranded is a few dollars per unit and several years of life.Ask for the model numbers. If a quote cannot name them, the answer is probably that they change with each batch, and so will your spare parts.
Line 5: "3 years warranty"
Three years on the panel is not three years including parts, labour and freight.Ask whether the backlight is covered, whether replacement ships from stock, and who pays the technician. A parts-only warranty can cost more over five years than a higher price with on-site support.
The comparison sheet we send clients
Panel grade and pixel standard. Board model numbers. Bracket type. Calibration included or not. Installation included or not. Warranty scope. Spare availability in years. Lead time.When a quote is 30 percent below the others, one or two of those lines explains it. Sometimes it is a fair trade. Usually it is the line the buyer did not read.