Do you decide which projects have to be developed first based on the monetary benefits the business will receive or follow business priorities regardless of project costs? 

It’s a mix of box but business priorities and clients wants have a lot of weight on how we prioritize projects

It really depends on the situation but mostly Business Priorities drive the project schedule. In some extreme cases the project may be set for two phases, Phase 1 to immediately fulfill Business Need and phase 2 to realign the project for cost effective method & technology.

The 2 should ultimately align if governance is done properly, but in any case, we generally follow and work on things in order of business priority. If business priority is to maximize monetary benefits via a project, it should be at or near the top of the priority list.