Also, animate dead costs 25 gp per smashed HD (whoever believes that skeletons and zombies -edit: including the bigger HD ones .edit end- last long in level 12 combat better should check out the CR 12 creatures... ).
I take it you've never played a necromancer then? I have. Let me explain.
When I used a Dread Necromancer most recently (at level 12, in fact) I had Corpse Crafter in addition to Undead Mastery, and always raised my undead in desecrated areas (there's a ring that provides this). As such, my undead always had D12+6 HD. A really solid undead would be a 10 Headed Pyrohydra zombie... 250 hitpoints, 10 attacks, reasonable enough AC (not amazing, but reasonable). In fact, all my zombies had 250 hitpoints (all my skeletons had 125), except for Zombie and Skeleton Dragons, which don't have the usual hp cap (thanks, Draconomicon!). And as undead they of course had a horde of immunities that really helped. Additionally, I used Black Sand and had some on each of the undead, so they all effectively had Fast Healing 1d6, in addition to support from Necrosis Carnexes (MMV) which auto heal nearby undead. And to be clear... the only difference between an Adept doing that and a Dread Necromancer is that the Adept's undead have 40 less HP (for Zombies) and 20 less HP (for Skeletons).
Now compare that to the Monks you've build and shown us in various threads. How many hitpoints do they have? How much do they self heal? How many save or die effects are they immune to? How many save or suck effects are they immune to?
It's funny that you think Monks can survive that level of play, and then turn around and claim undead can't.
JaronK