Abstract In Extended Conceptual Metaphor Theory (Kövecses, 2020), I offered a comprehensive overhaul of “standard” conceptual metaphor theory. The present paper attempts to demonstrate how the new view of CMT can handle metaphorical idioms. To this end, I analyze four metaphorical idioms from the thematic area of money (throw money about, money slips through someone’s fingers, be a cash cow, money keeps someone/something afloat). The analysis assumes and starts out from the observation that money-related metaphors are based on two generic-level conceptual metaphors: money is a moving entity and money is a force. Extended CMT adds to CMT the notion of “mental space-level metaphors” that were largely ignored in “standard” CMT, but are given an important role in extended CMT. These are the metaphors that represent actual, contextual meanings in a metaphorical usage event. Traditional CMT-type analysis cannot account for the emergence of such idiomatic meanings because the mappings, or correspondences, of standard CMT work on a single, generic level (frame-, domain-, or even image schema level). However, the contextual meanings of naturally used metaphors (including those of metaphorical idioms) are much more information-rich and specific. The conceptual metaphors on the image schema, domain, and frame levels are offline structures in long-term memory, whereas the conceptual metaphors on the mental space level occur only online in working memory. In online communication, speakers mobilize the static image schema-, domain-, and frame-level metaphors at the mental space level, where they create highly specific mental space-level metaphors. Given this framework, it becomes possible to explain how and why the four metaphorical idioms have different contextual meanings (as represented by different mental space-level metaphors), but, at the same time, why they also share certain conceptual metaphors on the frame-, domain-, or image schema-level. Additionally, we gain new insight into how the emergence of novel metaphorical idioms occurs with the help of and constrained by a previously existing large system of hierarchically arranged conceptual metaphors.