The amount available isn't even what bothers me. Basically just the fact that it's legit only available to AD champs by default, whereas the average AP has to sacrifice something to even have a chance at it.
The items increase their auto damage, their ability damage(For AD scaling skills.), AND they have lifesteal available - Meaning they're useful with or without their skills, and are able to heal back some of the damage they take. Whereas anything available to AP increases their spell damage(Similar amounts to AD champs - It's not like their spells are inherently stronger in many cases), without doing anything for their auto attacks, and don't offer a comparable form of healing - Meaning once their rotation is down they're just a sitting duck who's auto attacks hit like a limp noodle in most cases.
I get that the game has been balanced around the things I state, and AP champs -TEND- to have more utility, or offer more CC, or have shields, or whatever, that AD champs often don't have in their kit... But it's really frustrating that there's just no viable method of sustain for an AP champ. If I'm down to 30% health I -NEED- to back if I want to heal up on the average AP, whereas the average AD will build some form of Lifesteal and be able to heal simply from killing the next wave that comes through.
On the flipside they don't tend to have mana sustain for most AD champs, with very few options in their itemization to change that - But many of them have lower spell costs/less spell reliance, and they have the ability to still do decent damage with their autos even if they DO run out of mana.
In a perfect world(IMO) all skill damage would scale off AP(Note: ABILITY Power.)[Except possibly some fringe cases for various reasons, such as defensive skills scaling off of defensive stats], and all autoattack damage would scale off AD(Note: ATTACK Damage), which would then allow people to build to suit their needs - Am I going to rely on my abilities? My autos? Both? But this would require a rebalancing of the entire game from the ground up, and just isn't a viable idea for something that would actually happen. I feel it would be significantly easier to balance the game if it had been this way from the start though, as items(And thereby item effects) wouldn't be as useless in as many cases as they are right now.
Like I said, never gonna happen, but it's something I've thought about a few times throughout my league career while watching Zed throw out his strong spells, miss half of them, then proceed to just Auto me to death anyway because all of his options scale from the same stat, whereas the AP champs I play only really get their spells due to their autoattacks being basically a mosquito bite.
isn't a thing.
And neither is 
+
+
+ 1050g (3100g)
Total stats 80 AP 10% CDR 300 Mana 10% Spell Vamp 5% Move Speed.
+ 950g (3400g)
Total stats 100 AP 10% CDR 300 Mana 10% Spell Vamp 5% Move Speed.