All D&D Miniatures (well, of the current line) are Prepainted Plastic Figures. They are assorted randomly, so in a expansion pack you get 8 random figures (1 rare, 3 uncommon, 4 common). In the
Giants of Legend pack you'll get 1 rare, 3 uncommon, 4 common and 1 huge.
The Huge figures may be either of the Rare Huge or Uncommon Huge rarity, with a 1:3 ratio of Rare : Uncommon Huge figures.
You don't need the MHb to play the game, all you need is the D&D Miniatures Entry Pack - the MHb is half D&D RPG and half D&D Miniatures.
The mass-battle rules in it are disappointing, the skirmish rules are excellent.
D&D Miniatures retail for $9.99 for 8, although the price is increasing to $12.99 for 8 in the near future; the Huge packs will retail for $19.99 each.
More information on my site, including set lists, galleries, spoilers and more.
Cheers!