Sorry, I'm thinking about stepping up to Emperor, but just to make sure:
When you hear that one of the differences between Monarch and Emperor are this:

MONARCH
research ×1.15
unit cost ×0.70
distance maint. ×0.90
civic upkeep ×0.95
inflation ×1.00
AI costs ×0.90

EMPEROR
research ×1.20
unit cost ×0.80
distance maint. ×0.95
civic upkeep ×1.00
inflation ×1.00
AI costs ×0.85

then I have two questions:
1. the "AI costs" line refers obviously to some bonus in expense for the AI, but I dont know exactly what and how it factors in to those other things listed above. WHen I see "AI costs x 0.85", does it mean that the AI pays only 85% of hammer costs for all production queue things, only some production queue things, or also for research, maintanance, war weariness, civic upkeep, inflation, and/or something else too?
2. The items listed above seem clear enough, but just to make sure: If "research x1.20" in Emperor seems to be what it implies, namely, that I (the player) pay 120% of beaker costs for techs in emperor (as compared to 115% in Monarch) -- but is this COMPARED to the AI or absolute? I mean, does this x1.20 mean that ALL players in the game (AI too) pay 1.20, and then the AI gets a .85 break later, or that ONLY the human player pays 1.20 (and then possibly the AI gets a .85 later, see question 1)?

(I know the main challenge to Monarch comes with the additional settler and other units the AI gets, my question is merely about the other stuff listed for all difficulties)

Thank you

It means the AI will build a 100 hammer building for 80 hammers, a 100 beaker tech for 80 beakers, and if you would need 100 food to grow the AI would need 80. I think it applies to every visible variable BUT wonders, gg/gp points and experience. You research a 100 beaker tech for 120 on emperor.

Disregard. Dan is more sensible.

e: and the AI ONLY gets an extra settler at Deity.

....and that darn extra settler is a real killer early on! :vomit:

1. the "AI costs" line refers obviously to some bonus in expense for the AI, but I dont know exactly what and how it factors in to those other things listed above. WHen I see "AI costs x 0.85", does it mean that the AI pays only 85% of hammer costs for all production queue things, only some production queue things, or also for research, maintanance, war weariness, civic upkeep, inflation, and/or something else too?

85% refers to production (except of wonders) and research. Inflation, war weariness, civic upkeep and so on have separate AI modifiers that you haven't shown in your post. The AI does receive bonuses to these other parameters at high level, but they will not necessarily be the same percentage as the production and research bonuses.

2. The items listed above seem clear enough, but just to make sure: If "research x1.20" in Emperor seems to be what it implies, namely, that I (the player) pay 120% of beaker costs for techs in emperor (as compared to 115% in Monarch) -- but is this COMPARED to the AI or absolute? I mean, does this x1.20 mean that ALL players in the game (AI too) pay 1.20, and then the AI gets a .85 break later, or that ONLY the human player pays 1.20 (and then possibly the AI gets a .85 later, see question 1)?

All of the lines you've quoted refer to absolute costs, not costs relative to the AI. E.g: research at 1.15 at Monarch means that all players are paying 15% more for each tech than at the 100% level (which happens to be Noble for the research cost). The AI cost of 0.85 means the AI is paying 85% of that 1.15 research. The AI therefore is only paying 85% of the amount the human player does, but the base cost of the tech is higher at monarch than at noble.

The unit cost, inflation and so on also have base modifier values which increase for all players with difficulty level (these are the ones you have quoted, and so the numbers in the OP do not reflect AI bonuses). There is a separate set of AI values (listed as AIUnitcostpercent, AIInflation and so on) in the XML files which indicate the bonus the AI has over the human.

(I know the main challenge to Monarch comes with the additional settler and other units the AI gets, my question is merely about the other stuff listed for all difficulties)

The AI doesn't get an extra settler at Monarch. That appears only at Deity level. At Monarch the AI just starts with a free archer. At emperor, they get two extra archers and a scout.

CIV4HandicapInfo.xml has all the numbers.

Some of them for Deity level:
<iAIWorkRateModifier>100</iAIWorkRateModifier>
<iAIGrowthPercent>80</iAIGrowthPercent>
<iAITrainPercent>60</iAITrainPercent>
<iAIWorldTrainPercent>100</iAIWorldTrainPercent>
<iAIConstructPercent>60</iAIConstructPercent>
<iAIWorldConstructPercent>100</iAIWorldConstructPercent>
<iAICreatePercent>60</iAICreatePercent>
<iAIWorldCreatePercent>100</iAIWorldCreatePercent>

means:
Workers improve land @ double speed
Cities require only 80% of food to grow
Units/Buildings/Projects cost only 60% of hammers ("train"/"construct"/"create")
no bonus for World Wonders/Projects/Units(?)--I don't know what a World Unit is ???

I like to investigate AI cities (WB Great Spy) to find those things out, though I do not like what I see.
Deity Capital @ Turn 1:
http://i294.photobucket.com/albums/mm105/DanF5771/Civ4ScreenShot0005.jpg

Edit: The research shown in the picture is actually MY research, because Darius has not chosen a tech yet (just founded Persepolis). Also the mouseover over current research in an investigated city will always show MY research.

MrCynical: I thought AI players would always play @ Noble difficulty and hence also always research @ 100% without any modification (OK 0.85*1.15 ~ 1 @ Emperor, but 0.6*1.3 = 0.78 < 1 @ Deity ???).

Thank you, that is very helpful. Probably to more people than just me.
Sorry, in my original post my last line in brackets was a total mistype; I play monarch now and was thinking about going up to emperor.
I am not entirely sure I understand why the numbers appear to be slightly different in the data I have (which I merely obtained from the .pdf sheet by Anion on this website) and your data, but I will try your idea with a WB and a spy in a new game.
Thank you