The cost to develop a B2B eCommerce app can vary widely depending on a number of factors such as the complexity of the app, the features and functionality that are required, the development team you hire, and the platform you choose to build the app on.
An MVP (Minimal Viable Product) B2B eCommerce app with a basic number of options and functionalities could be built for even less cost ($10,000 - $20,000). Yet, with the addition of complex features and such as integrations would definitely make the app cost $50,000 to $100,000 and above.
Yet, although the development price is not the sole price to evaluate, building a B2B ecommerce application can cost more than other e-business applications. And to create a functional budget for the constant upkeep and support, hosting, marketing and other expenditures should be a part of the budget as well.
It is critical to have a comprehensive clarification of work you seek for, desirable features and functionalities of the app, and approved budget, to have precise estimation, plan and decide.