I am playing in my test company with pricing.  I entered a customer contract price for an item in SO-Q-H.  Then I went to the enter price code, SO-Q-D to enter a price code for a different item.  In the opening screen, the contract price is listed and there are no ADD, EDIT etc buttons at the bottom of the screen.  If I highlight the contract price, it explains that this is a contract price not a price code and I need to go to contract price to delete it!  If I go to contract price and delete it, when I go back to SO-Q-D I have the full screen back with nothing listed and all the buttons to add, edit, etc.  
Then I tried to enter a price code first and then a contract price.  The same thing happens in reverse.  
Is this a glitch, or is it that once you enter one contract price, you can no longer have any price codes and vice versa?  
Also I notice that the line about overwriting existing codes, [S/R/C] is skipped over entirely. I don't really know how to answer this question, but I also wonder why I don't get a chance to!

I can't see how to enter either when I have entered the other.  Even with only one contract price or price code entered, I lose all the buttons, including the add button, in the other one, so how am I supposed to enter one?  There must have been some change after you were able to enter both, and now since you have both the program is working correctly for you.... but not for those of us that need to enter them. Any one else experience this?
As for the S/R/C question, who knows?