I like how this movie has cost $7000 and brought in nearly $500,000.
Why is this an important distinction? Because you can't calculate or quote business investment and return while discarding the cost of people working for several years on a project for free.
Saying that Primer cost Shane Carruth $7000 to make is like saying that The Harry Potter Book Series cost J K Rowling 19 ink cartridges.
It's important to appreciate what Shane achieved with such few resources though, and it's interesting to note also that he was a software engineer before making his way into filmmaking.