It seems you have forgotten that Axes are accessible.
in the 1.8 mode you cannot get them, so maybe make this a only 1.9 feature idk
I really like the idea to be able to buy mobs, it would make the game pretty fun and interesting. I'm not sure if these mobs will work in EggWars however.
only problem is that they need bridges or you could just fly and spawn them while maybe feeding them bones to protect you as you mine the obsidian :D
Beasts: 5 Bones (64 iron)
i think wolves should not be tamable at all, this will bring a brand new strategy, place the wolf where your enemy is hitting so the wolf is triggered at them, if you hit them they attack you, but they need an HP buff cause they could easily die, but the being triggered to anyone who hits it will balance it out and make the enemy unable to use their own wolf egg or that wolf will attack him
Beasts: Horse egg (64 diamonds)
Beasts: Saddle (64 diamonds)
Beasts: Iron horse armor (64 iron)
Beasts: Gold horse armor (64 gold)
Beasts: Diamond horse armor (64 diamonds)
i don't like this for several reasons, unsafe to cross bridges, can suffocate which means maps have to be remade to make it "suffocation free", people will be too fast and cannot be able to kill them, the horse can spawn with a 'natural gift' of being able to jump high or be faster than others which are unfair and could cause more camping
Blocks: Cobble wall (5 iron)
no point with this because decorating isn't part of eggwars, just use other blocks to make a wall
Blocks: 2 Slime blocks (10 gold)
we already have hay bales so no use in this because hay bales reduce fall damage and DON'T send you back flying able to kill your enemy
Archery: 16 healing 2 arrows (32 diamonds)
No point in this because you cannot shoot yourself so you will be helping enemies
Blocks: Birch wood plank (1 gold)
for the 1.9 feature of eggwars YES! because it will encourage people to use axes or carry them, in 1.8 this shouldn't be a feature, but you could also use hay bales since there is no special item that makes you mine it faster
miscellaneous section: Water bucket (64 gold)
this is just too much
people can place it above the villager and move him with the water, place it where you shouldn't, cover your entire island with water to troll and make it unable for players to get in it, people reaching sky limit, placing water and getting to the bottom of your base in a few seconds, encourages more camping to grind for this
Armor section: Elytra (64 diamonds)
i am neutral with this, but maybe to balance it have it have X durability, this idea itself has some pros and cons but the enderpearl could do for now