First, let's deal with weapon enchantments
If you add enchantments one-at-a-time the Xp cost will always be 80 for +1 equivalents and 320 for +2 equivalents.
If you add all enchantments at the same time the base xp cost is 80 for +1, 320 for +2, 720 for +3 following this table:
+1 = 80 , add 240 (80 + 160) for
+2 = 320 , add 400 (240 + 160) for
+3 = 720 , add 560 (400 + 160) for
+4 = 1280 , add 720 (560 + 160) for
+5 = 2000 , add 880 (720 + 160) for
+6 = 2880 , add 1040 (880 + 160) for
+7 = 3920 , add 1200 (1040 + 160) for
+8 = 5120 , add 1360 (1200 + 160) for
+9 = 6480 , add 1520 (1360 + 160) for
+10 = 8000, maximum enchantment level.
As you see, adding enchantments one at a time costs less Xp, a 240 xp cost for a +3 blade vs 720 xp cost if you make it in one go.
The price in gold follows this table:
+1 = 1.000 GP
+2 = +3.000 GP
+3 = +5.000 GP
+4 = +7.000 GP
+5 = +9.000 GP
+6 = +11.000 GP
+7 = +13.000 GP
+8 = +15.000 GP
+9 = +17.000 GP
+10 = +19.000 GP
These values stack, so making a sword + 3 costs a total of 9.000, (1.000+3.000+5.000) and adding the
Flaming ability would cost 7.000 more gold.
The 3.5 rules state that maximum enchantment bonus is +5 in "plusses" and +10 in total enchanments. In TOEE plus bonuses is maxed at +3, but you can still add special abilities up to a +10 in total bonuses.
The special abilities has + equivalents as follows:
Flaming = +1
Frost = +1
Shock = +1
Keen = +1
Mighty cleaving = +1
Anarchic = +2
Axiomatic = +2
Holy = +2
Unholy = +2
Icy burst = +2
Shocking burst = +2
Flaming burst = +2
So a +3 sword could have +7 in extra abilities added, i.e Holy, Axiomatix, Flaming, Shock and Frost. It's then treated as a +10 weapon. (for things as resale value & max enchantments)
If you try to add more the game is likely to crash, but it may work if you add +3 first, then Bursts and last Holy/Flame/Frost/Shock.
Also, according to the rules a Icy Burst weapon is also a Frost weapon, Flaming Burst is also Flaming and Shocking Burst is also Shock. AFAIK these effects shouldn't stack but TOEE let's you put both on.
The damage from Frost is "cold" but the game treats damage from Icy Burst as "negative_energy", so these two stack anyway.
I don't know the Flaming/Flaming Burst and Shock/Shocking Burst combos, but IMO they shouldn't work. Anyone else know this ?
[edit] just found out that flaming/flaming burst also work and you'll get 2d6 fire dmg. instead of 1d6. Cool!
Now, for Armor & Shields:
If you enchant armor or shields to only +1, you won't be able to add +2 and +3 later. This is a bug, so make sure to enchant up to max +3 in one swoop.
+1 costs 500 GP, and 40 Xp
+2 costs 2.000 GP, and 160 Xp
+3 costs 4.500 GP, and 320 Xp
Sadly, only two abilities for Amor and none for Shields:
Silent Move = +1, costs 3.500 or 5.500 GP, Xp 40
Spell Resist(13) = +2, costs 8.000 or 10.000 GP, Xp 160
The two cost are for which order you add them, so adding both will cost 13.500 GP and 200 Xp total.
Last, remember that although Spell Resist(13) is bugged, it adds to the resale value of armors, meaning you get a LOT more gold for selling
Also, to enchant Flaming Burst you have to cheat by editing your item_creation.mez file found in your TOEE/Data/Rules folder.
Hope this helps