Sturdy cardboard box for storage of about (1000,4000 or 5000) standard sized cards.

NEW 1600 Count 2 ROW Toploader Storage Box

You can also store sleeved cards.

Those boxes were initially designed for Baseball- and Sportscards in general. TCG players, collectors and sellers use those boxes for years and they have proven to be useful in organizing big quantities of standard sized or smaller TCG cards.