I have a short brown bag presentation I give at employers who aren't sufficiently enlightened about open source. I start by showing the amount of code we've written as a company - for a software start up, that might be on the order of 100k lines of code. I'll show a slide representing this amount of code as one or more boxes. I'll make some arm-waving equivalence between that, and the amount of $ revenue we earn from it, or the number of person hours it took us to write it.
Then…