Usually the discounted designer glasses you can get are not the lastest style , some retailers will sell them in low price to reduce the stock . Also you can get some cheap D&G eyeglasses online such as net-a-porter which sells designer products
Oh, Dolce&Gabbana designer glasses are expensive. Maybe you can try to get it on ebay for a low prices. Or you can try to buy some stylish glasses that have the same look as brand designer one but priced at cheap prices. There are many eyeglasses shop you can go such as Firmoo.com, framesdirect.com or zennioptical.com. And i saw there are many new stylish and cute glasses at Firmoo. Just have a try.