Why are Rigid Letters so much more expensive?

The acrylic that most rigid letters are printed on is a higher quality, with additives that protect them from weathering, turning yellow and getting brittle. These are often designated DR (Rohm & Haas). Another obvious reason is because the rigid letter plastic is thicker, but it's the type and treatment of the acrylic that accounts for most of the added expense. The cost is more, but the result is a letter that lasts 10 times longer. Rigid letters are more often used in overhead signs, out of reach. This, combined with the different track configuration, means they probably won't need replacing very often, which justifies making them more durable. Flex letters should normally last around 3 to 5 years, and sometimes longer depending on care and how often they're changed. Because they are used in ground level signs, the lower price makes them more attractive when replacement is needed due to factors other than age. Standard flex letters should never be used on an enclosed sign (a sign with doors on it).