The word "costlinesses" refers to things that are expensive or costly. However, there are several synonyms that can be used in place of this word. These include terms such as lavishness, opulence, extravagance, luxury, and splendor. Each of these words conveys a similar sense of sumptuousness and expense, but may be used in different contexts. For example, lavishness might describe a party with expensive decorations and entertainment, while opulence could refer to a grand palace or mansion. Regardless of the synonym used, these words suggest a level of wealth and abundance that is not typically within the average person's means.