I have made pocket nappies twice and they were pretty easy.
Check out
The Nappy Network for free patterns and
GreenBeans for material.
From memory I think it might have cost me about $10 to make a pocket and hemp/microfibre combo insert, or maybe it was cheaper than that?
They aren't hard to make although I did get MIL to make my last lot but that was because I didn't have time. The first pocket I made was a ittle hard as I didn't have any of my own so wasn't 100% sure how they were made