When something requires a significant investment, it can be described as pricey, expensive, or costly. Other synonyms for the phrase "of great cost" include high-priced, dear, premium, exorbitant, extravagant, and valuable. These terms can be used to describe anything from a luxury item, such as a diamond necklace or a sports car, to a more practical purchase, like a house or a new computer. Regardless of the context, using descriptive language to communicate the value and expense of something can help to create a more nuanced understanding of the item's worth and the level of investment required to obtain it.