Start by trying not to build
The cheapest software is the software you configure rather than write. If an established product covers eighty per cent of the process and the remaining twenty per cent is negotiable, buy it.
Three signals that custom is right
The process is genuinely differentiating and copying a competitor's tool would erase the advantage.
Licence and workaround costs already exceed what building would cost over three years.
The team maintains a critical spreadsheet that no vendor tool can replace.
Budget for the second year
Custom software has an ongoing cost: hosting, dependency updates, security patches and change requests. Plan for it, or the system quietly rots.