"If we knew what we were building, it wouldn't be called research!"
Sufficiently advanced mathematics is indistinguishable from magic
For a specific example: suppose Rowena has built a size-2 device consisting of a Clockwork Source and a Librarifier. This is a nice device but it's getting less useful now that the Age II belt is open. She goes and plays in Alice's Sourcer. Alice gets a clock counter and £1. But the result of that action is that Rowena gets to add a Steam Source from the general supply (not her own personal supply) straight into her Librarifier. Now the device has two ways in: a Clockwork Source for taking tiles from the blue Age I belt, and a Steam Source for taking tiles from the white Age II belt.
Edit: As Argenfarkle said. Originally my example used the Upgrader which is a great example of a component that benefits from the Sourcer, but its effect is somewhat similar and I didn't want to confuse things by implying that the Upgrader and Sourcer are related. They're just different ways to accomplish somewhat similar things.