Why does nobody talk about the library sale rack for cheap kids books

A coworker on my unit said the library sale rack at the Main Street branch puts out kids books for a quarter on the last Saturday of the month, and I figured that was too good to be true. I went last weekend with $5 in my pocket and walked out with 18 books for $4.50, which is less than one new hardcover at the store. Turns out they clear the donations table before the big monthly sale and anything left gets dumped in the quarter bin, so you just have to get there early since the good stuff goes fast. Has anyone else hit up a library sale like this, and do you go right when they open or later when they mark stuff down even more?