Think of employees as subcontractors. Their basic monthly salaries are your costs of having them on standby to work on your assignments. Then you can (more or less) calculate the value of a unit to your company / project and that's what you pay for it. Roughly speaking. So "unit" won't translate into "work unit" (like LoC and similar quantities) but into "subproject". And so we're talking about capital budgeting. A good hacker can understand and apply this creatively after some good books or courses (or the VC advisors provide the knowledge), 'cause in the end it's just some basic concepts + formulae.