It is not not easy to say how much the plastic sunglasses sold in Walmart as there are many types. Different types with different materials or even different design shall be different in price. So there are many prices. But for common ones it might ranged from usd 10 to use 40. If you are really interested you better go shopping in Walmart and have a look , that will make you more clear.
Or you can go to their website www.walmart.com for an impression first.
The plastic sunglasses' average price at Walmart is about $70. The plastic sunglasses are light at the weight which will make you wear comfortably. In addition, there are many types of such kind of sunglasses at Walmart. You could go to have a look and base on your favor to choose the suitable one.
As you know, plastic sunglasses' frame is made of plastic, which made their cost lower. However, their lenses are no different from other kinds of glasses on general. At Walmart vision center, where a lot of glasses are available, you can basically get what you want at a relatively lower price since they are superstores you know?