Multiple cameras increasing draw call count immensely

I am using a simple multiple camera script, but am finding that the draw call count is going up from 50 to 500 when the script is enabled.
The script has worked before with no such effect.
Any ideas why this might be happening?

Are you sure you’re not re-rendering the scene? Make sure the render layers for each camera don’t overlap.
Camera A - BackgroundLayer
Camera B - Characters

So if Camera A was set to render everything and Camera B was also set to render everything you’ll be rendering the scene twice.