Ahh never mind then, you don't calculate like I do.
See, what I do (look around for the numbers I posted to find my desmos link to Ashe's numbers) is to first type out the damage variables of a given champion. For example, Ashe's Physical DPS comes completely from her auto attacks and her Volley, so my base calculations look like:
((97.6+AD)((1-C)+2C)0.658(1.68+AS)+(1/(4(1-CDR)))*(80+97.6+AD))(100/(100+Ar))
Now in order to find gold efficiency, all I need to do is find out how much damage Ashe currently does (In this case, with no items to her name, she does 152.290944 damage before Armor reduction) and divide the difference by how much gold a given item is worth. For example, the Infinity Edge would look like:
((((97.6+80)((1-0.25)+2.5*0.25)0.658(1.68)+(1/(4))(80+97.6+80))(100/(100+x)))-((152.290944)(100/(100+x))))/3800
Where we have [[Ashe with Infinity Edge]-[Ashe without items]]/[Cost of Infinity Edge]. I also changed the armor variable to x so we can move on the next step: Graphing.
Basically, I use https://www.desmos.com and simply plug in the calculations I have here. I find Desmos to be great for this sort of work because it color codes each graph and you can stack multiple graphs onto it. For example, this is a cross-reference between the Infinity Edge and the Spirit of the Elder Lizard.. You'll see that the Black Line, the Spirit of the Elder Lizard, has a greater value than the Orange Line, the Infinity Edge, any point after the opponent has 196.3 Armor.
EDIT: In my genius, I forgot that the Boards use asterisks for bolding/italicizing. I hope you can still read these calculations without asterisks.