After Valve reduced the price of the AUG, everyone started exploiting the power of this weapon. The CS:GO community were begging Valve to nerf the AUG and get back the old price. Thats what Valve did in the last the CS:GO Update Meta Change. Alongside the AUG nerf, Valve made one significant economy change.
Source: N4G PC CS:GO Update Meta Change: AUG Finally Nerfed, Big Economy Change