The cost of any BI project is dominated by the time and effort put into ETL and data modelling. 80% of our effort goes toward this back end work. With this in mind, the presentation layer is essentially an afterthought. The lion's share of BI cost goes to expensive humans. If you can spend a few $100Ks for presentation tools that integrate seamlessly with the back-end analysis services and streamline report design/publication, then it's a no-brainer.
With technical employees/consultants at a premium, and in short supply (especially in the data modeling space), it is worth $100Ks annually to have a toolset that allows non- and minimally-technical employees to quickly and easily build new reports.
Take a look at Microsoft's PowerBI dashboards, or at the visualization capabilities in Tableau. The functionality there is what businesses want/need.
Those tools and Plotly equally require a solid data warehouse behind them to support any meaningful and timely analysis. The marginal cost of a highly-integrated and easy-for-non-technical-resources reporting layer is pretty low after that investment.