Marquees can be made out of either glass or plastic. Glass marquees tend to be worth more, due to their fragile nature. The condition of a marquee can greatly affect the price. Marquees that have been cut down have little value. This was sometimes done when converted or to hide some flaws.
Cracks also tend to limit the value of marquees.
Some arcade owners would order extra marquees to have in case the one on their machine was damaged. NOS marquees should have the paper still on them. If it wasn't stored properly, it could still be damaged. Inquire before purchasing. Remember that these prices are just an average of the market price.