Well we had a thread on dungeon drops and unfortunately most of those aren't still sought-after or applicable today (or the skill books didn't exist at the time), but the older monster drops are still wanted for various reasons nowadays so let's look at those.
Monsters with drops generally have three drop pools* with a weighted chance of each pool being selected when the monster drops something. Whichever pool is chosen, they'll pick one item in the chosen pool. Devcat further weights the odds of certain things by putting them in a pool more than once.
* - For a number of monsters, pools 3 and/or 2 have nothing in them with a weight of 0.
So the monster has a ~63.38% chance to drop the glowing ear part.
Pool Weight Chance Item Item Item 1 600,000 ~95.08% Phoenix Feather Stone Hound's Glowing Ear Stone Hound's Glowing Ear 2 30,000 ~4.75% MP 30 Potion - - 3 1,000 ~0.15% Elite Magic Powder - -
And the end glowing statue monster has a 2/3 chance to drop the page, further showing how the RNG hates me.
Pool Weight Chance Item Item Item 1 600,000 ~100% Exploration Journal, Page 3 Exploration Journal, Page 3 Quartz Light Leather Mail (M)
Anybody gotten annoyed at collecting those Volcano Lizard Scales? Well it turns out there's two kinds of the lizards. There's VolcanoLizardA (green) and VolcanoLizardB (red) and they have similar drop pools, but small differences and different weights that result in different chances of a scale.
Pool Weight Chance Item Item Item 1 190,000 ~85.97% Volcano Lizard Scale Sliced Meat Stamina 30 Potion 2 30,000 ~13.57% Empty Bottle Arrow (10-40) Fossil 3 1,000 ~0.45% Tork's Hunter Gloves - -
So the green ones have a ~28.65% chance to drop it, while the reds have a 22.95% chance.
Pool Weight Chance Item Item Item Item 1 240,000 ~91.95% Volcano Lizard Scale Sliced Meat HP 30 Potion Stamina 30 Potion 2 20,000 ~7.66% Phoenix Feather Arrow (10-40) Fossil - 3 1,000 ~0.38% Stiff Hat - - -