Many mod developers do not charge for mods however some fee's may be charged if a bukkit plugin needs to be specially coded however it is choice of the coder how much they want to charge you.
Usually, a mod is free. I have not seen any mod wich costed money.
Its free
No
Well, you need the game 'minecraft' which does cost money. Pixelmon is just a mod for the game 'Minecraft'.
Its Free
You can't mod the console version.
Nope. You HAVE to download a minecraft mod to have it.
a mod where you can fly a plane on minecraft so get it
Minecraft doesn't have an official best mod.
Mo Creatures is a modification (mod) for Minecraft. You can get this mod by downloading it from The Minecraft Forums.
One example of a superhero mod in Minecraft is Superheros Unlimited for version 1.6.4.
free, just google