AI has made it dramatically faster to prototype an internal planning tool, which has revived the build-vs-buy debate for finance infrastructure. But prototyping speed and the total cost of owning a system long-term are two different questions, and only one of them has actually changed.
Why AI changed the prototyping conversation
A small team can now stand up a working planning prototype in weeks using AI tools.
What hasn't changed
Ongoing maintenance burden
Someone still has to patch, monitor, and rebuild the tool every time an upstream system changes.
Data governance and security
Access controls, audit trails, and compliance requirements don't get lighter just because the build was fast.
Integration with the rest of the stack
Connecting reliably to the ERP, CRM, and HRIS is still the hard, unglamorous part.
Decision framework
Narrow, low-stakes tool
→
Build
Core financial infrastructure
→
Buy
Uncertain long-term ownership
→
Buy