Ask HN: How many people, time and budget did you need to build your backend?

Hey there! I'm interested in understanding what is the typical investment (in terms of people, salary, and time) to develop a backend solution (leaving maintenance aside). I'd also be nice if you can roughly explain the scale and complexity of the backend solution you built. For example, I worked on a knowledge-graph backend solution consisting of an API and N workers consuming tasks from a queue that took ~2 years to develop, 3-4 full-time backend engineers and a total investment of around 300k USD.