For, At ... Off, Less

[boscht]

Suppose a book, originally $50, is now on sale and $45. Then someone bought the book:

"He bought the book for 10% off."
"He bought the book at 10% off."
"He bought the book for 10% less."
"He bought the book at 10% less."
"He bought the book for 5 dollars off."
"He bought the book at 5 dollars off."
"He bought the book for 5 dollars less."
"He bought the book at 5 dollars less."


Are some of them wrong?

[Chicken Sandwich]

Gee whiz, this troll just doesn't know when it's time to call it quits . Is this really your definition of a good time?

[bhaisahab]

Gee whiz, this troll just doesn't know when it's time to call it quits . Is this really your definition of a good time?

Gone.