alt Hacker NewsThe only approach that genuinely works for software development is to treat it as a "bet". There are never any guarantees in software development.
1. Think about what product/system you want built.
2. Think about how much you're willing to invest to get it (time and money).
3. Cap your time and money spend based on (2).
4. Let the team start building and demo progress regularly to get a sense of whether they'll actually be able to deliver a good enough version of (1) within time/budget.
If it's not going well, kill the project (there needs to be some provision in the contract/agreement/etc. for this). If it's going well, keep it going.
How would you decide between doing project (a) this quarter, or project (b)?
If you cannot (or refuse to) estimate cost or probability of success in a timebox you have no way to figure out ROI.
To rationally allocate money to something, someone has to do the estimate.