You are absolutely right.  Cheap sunglasses do not offer complete UVA & UVB protection.  Cheap sunglasses block some light and allow your iris to open, which increases the exposure to UV rays.  While you don't need to spend $200 on a pair of sunglasses, just make sure to ALWAYS purchase a pair with 100% UVA and UVB protection.  If you don't, you are a fool. And Herman, typically when one purchases a pair of $200 sunglasses, they tend to make sure they do not lose the $200 pair of sunglasses.  
 
 
My eyes get real sensitive to sunlight when I have my contacts in.  $200 on a good pair of glasses is well worth not getting migraines.