One think I’ve never understood is the original 320 wing could not support blended winglets…whereas Boeing has offered them for years either from the factory or through a kit offered by Aviation partners.
A week out of service and $500,000 and you get 2-3% fuel savings.

http://www.aviationpartnersboeing.com/products_list_prices.php

I was going to disagree with your price assessment from memory, but having checked the figures, the quoted prices are generally above $1,000,000!!!