There are very good but at the same time cheap sunglasses. They are normally approved by some known agency. But unfortunately no company promotes these in Sri Lanka. They are as good as any other on quality, but these are not from reputed brand so may not be stylish. These type of sunglasses approved by some agency are available in other countries. Try to get such one from abroad.(this is similar to TRC certifying radiation levels of phones used in SL)
It is high time Sri Lanka standard or government introduce some standard to this industry.
A good branded one is always may be 25k but to make a UV cut sunglass is fraction of this , you can get UV cut glass for windscreen for less than this amount! So it is brands that had lifted prices not the cost.