Years of conversation fill a ton of digital pages, and we've kept all of it accessible to browse or copy over. Whether you're looking for reveal articles for older champions, or the first time that Rammus rolled into an "OK" thread, or anything in between, you can find it here. When you're finished, check out the boards to join in the latest League of Legends discussions.
As demonstrated: sometime before you have 50% crit chance, and after you have 135 base damage, it's better to spend 100 gold on raw damage, rather than crit.
You seem to think damage is calculated as "base damage minus armor = damage".
That's very rarely the case in games. Particularly if you mouse over the armor rating on your UI and it says "reduces damage by X%".
30 flat armor pen against a target with 30 armor is, I think, a 43% damage boost. A 43% damage boost is rather significant.
Touche on armor pen, I probably don't understand how it works but it's still situational. I'll research it if I have time tonight.
To the other calculations:
I'll say it again, it's not a pure DPS calculation, it's a value calculation. Meaning, did I get the most for my money? The most damage, crit, whatever. Did you get the most? In this case, you're comparing purchasing raw AD or manufacturing your own AD through CS. It's like a make/buy decision in the software development world.
5 AD is 175 gold. 7% CS is 350 gold. I suggest you revise your analysis here with the more relevant:
"130 AD, 1 AS, 13.5% CS = 147.55"
In case this isn't clear enough, you are comparing one unit of investment into AD, and DOUBLE the investment into crit%. Certainly, if you spend twice as much $$$ into crit, you will gain more DPS than half the $ into AD. Le shocke. Zen fire ze missiles~