Codified discounting solves pricing problems including markups and markdowns. The Text Verification Tool exports differences in documents as annotations and markups. Tracker Software's PDF-XChange Viewer allows annotations and markups without restrictions in its freeware alternative. Markups tend to be higher to the extent that oligopolistic firms have market power. Scalpers soon flooded eBay with pre-order listings, some at markups of over 300%. Street vendors in NYC are known to sell the glasses with extremely high markups. TransDigm was accused of spare parts markups during 2015-2017 as high as 4,451%.