Scroll to the very bottom of your list until you see "Pull to clear":
Pull the list from bottom to top until "Release to clear" text is displayed and release the list:
Another way to delete all the purchased products from a list is to tap the menu button in the top right corner of the list and select "Clear purchased":
Tap "Clear" to confirm the crossed-out items deletion, or "Cancel" if you've tapped "Clear purchased" accidentally:
"Pull to clear" and "Clear purchased" options are not available if you have no purchased (crossed-out) items in your list, i.e. if there is nothing to clear from your list.