Explanation: Roman tariffs actually varied - the standard transport tax within the Empire, the portaria, was 1/40th (2.5%), payable once at a local administrative center (typically a large city). There was a special import tax placed on the East, though, the tetarte, which was 1/4 (25%), mostly to take advantage of the high-value spices, silks, and incense that poured over the Eastern borders. By some estimates, the tetarte provided up to a third of the Empire's tax revenues! Which demonstrates both the value of the luxuries being imported, and the relatively low costs taken by the central government of the Empire.