All you need to do is send me details of the concept, a rough sketch(hand drawn and captured with phone) if possible & I will design a high quality diagram/infographic specially to cater your needs. Have it in print ready Adobe RGB/CMYK mode(300dpi) OR in web/device ready RGB mode(72dpi) OR both.
Simple ones will surely be for $5. But more complex ones need more time, thinking and efforts on my side which may raise the cost. Discussing about the actual task, approving the price quote & setting all deal conditions first will be a smooth modus operandi in my opinion.
I accept revision as an opportunity to make it perfect as per your need or to rectify minor errors overlooked at times. So, let the details flow in and get me busy!