Russian to English Other Military / Defense

From a documentary, an Afghan fighter is explaining how they would obtain weapons in battle. I'm not sure if this is a Russian saying or idiom. I haven't been able to work out the meaning of the sentence based on the meaning of the words or grammar. Here's the context:

В каждом бою мы добывали оружие. Воевать-то они не умели. Подходила военная колонна, останавливалась. ЗА ТЫСЯЧУ АФГАНИ ПРОДАВАЛИ ОДНУ ПОКРЫШКУ. Мы хватали у них оружие и убегали.