Just saw your edit. I did say anything OVER 1-1.1k is absurd in the current meta without lots of Gathering Power.
Something is fucky on that build though. You have 80CDR, 20 nashor's, 20 seraph's, 10 lichbane, 10 lucidity boots, 10 runic echos, and 10 transcendence. That's 40 over cap, which should be 80 AP, at 2 AP per CDR over cap. Why is it calculating as though it's 3 AP per 1 CDR over cap? Even if you have CDR stat shard, that's still only 100 AP worth of stats.
Not only that, but this build capitalizes on three things a lot. A ton of extra mana combined with seraph's and deathcap to compound it to a ridiculous level, plus the bonus (currently bugged?) AP from transcendence.
Let's do a thought experiment here with an absolutely ridiculous build.
Xerath, level 18, 833 mana.
If he has seraph's, death cap, luden's, spellbinder, zhonya's, and roa, transcendence, and eyeball collection (even though if he were going domination he'd take cheap shot)
He gets 58 from runes (including 20 from being 10CDR over cap, 20 from eyeball collection, and 18 from adaptive force)
3233 mana = 97 AP (96.99, close enough)
100 roa, 120 spellbinder/deathcap, 147 searph's, 75 zhonya's, and 90 luden's = 710 x 1.4 = 994 AP, with no boots, and a fucking spellbinder on Xerath. It would take 10 minutes of gathering power to break 1k.
The build you are using on Eve there, to capitalize on the factors I stated above, is not something of which most champions are capable. Even with a purely insane build on a traditional mage, it still takes a lot to break 1k AP. Gathering power, infernal drakes, etc. Getting above 1.2-1.3k takes even more. And, this is not even factoring in the notion that games almost never go beyond 30 minutes.
It is rare for a game to go to 6 items, even rarer for a game to go long enough to get a lot of gathering power. You said your elo is diamond, the average game time there is 27 mins. If we assume 150 gold per wave, no missed waves, that's 11,605 gold at 27 minutes, assuming no kills. 16,600 gold is required for that build. That means you'd need 17 normal-gold kills to finish it at 27 minutes, assuming no missed minion waves (can't be bothered calculating jungle gold). It's completely unrealistic and unreasonable.