When a customer hires a software development company, they sign a billing contract. The pricing model used depends on the project. The main models are fixed-price, time & materials, and milestone. In this article, we look at the advantages and disadvantages of these contract pricing models and tell you which is best to use when.
https://steelkiwi.com/blog/comparing-3-popular-pricing-models-fixed-price-time-materials-and-milestone/