The prudent vintner might well take a hard look at the cost of his slave labor as well. Columella criticized those who believed that any slave taken as war-booty and sold casually at auction could be turned into a worthwhile vinitor. Still, several Roman literary sources indicated that other kinds of skilled slaves, such as a good cook, could be bought for less than 3000 sestertii. As for the general work-force, vintners sometimes planned for the long-term, encouraging their slave women to have as many children as possible, even granting them freedom if they bore more than three sons. A babe-in-arms one year would be a nibble-limbed grape picker just a decade or so later.