How much does it cost to build a DEX?

I'm curious to know, what kind of financial investment would be required to construct a Decentralized Exchange, or DEX? Are there any standard costs associated with the development process, or does it vary widely depending on the specific features and requirements of the DEX? Additionally, what are some of the key factors that can influence the overall cost of building a DEX, and how can one go about estimating these costs in advance?