So, lets see:
Pig / Chicken / Cow / Spider / Zombie / Skeleton / ZPM / Creeper / Enderman
Spawner cost: $2,000,000 / $3,000,000 / $4,000,000 / $4,500,000 / $5,000,000 / $6,000,000 / $8,000,000 / $10,000,000 / $15,000,000
Money from one mob drop: $100 / $150 / $200 / $225 / $250 / $300 / $400...