When estimating timelines and budgets people frequently figure out what it costs to build something but forget the ongoing maintenance expenses.
A house might cost $200,000 but you also have to factor in ongoing costs such as taxes, insurance, general maintenance etc.
When dealing with software development people frequently forget the ongoing maintenance and scaling. Facebook or Google search each might have been coded by a few very smart people but they now take thousands of people to maintain them.
Don’t make the mistake of ignoring ongoing maintenance, upkeep and scaling when budgeting.
Have a great day!