From one beginner to another, here are the results of an experiment I tried concerning processors.

At the beginning of a game, I sent my 3 workers to mine a deposit of ore just outside the Line of Site of my Command Center. After about 5 minutes, I had 220 units of ore.

I restarted the game and sent the 3 workers back to mine the same deposit of ore except, this time, I had them build an ore processor next to the ore deposit. About 5 minute after start of game, even with the time spent building the processor, I had 370 units of ore.

All else being equal, that's a difference of 900 ore after 30 minutes of play. And the ore deposit was only 2.5 Command Center lengths away from the Command Center. Imagine the difference for anything further.

Conclusion: It is worth the price of carbon to drop a processor next to any significant resource deposit (food included).

SirKai