A (Water) 90,200 gp. Men.
All men are very lucrative, but much more so for water types. Buccaneers, pirates, and mermen are the apex monsters in terms of treasure. Interesting that the only magic item is a single treasure map, while the other A types have any three magic items. In fact, this is the only treasure type that specifies a map.
H 77,000 gp. Dragons only.
Very lucrative--the most lucrative if you only want to kill a couple of monsters rather than a couple hundred. Dragons should be the prime target of every rational party.
A (Desert) 48,800 gp. Men. Dervishes and nomads. Pretty good for magic items.
A (Land) 42,500 gp. Men. Bandits, berserkers, brigands. Also, cavemen.
Similar to their desert neighbors, but slightly fewer gems and jewelry.
G 24,500 gp. Dwarves only.
Lucrative in total, but only about 112 gp per dwarf on average. One of the best treasure types for magic items.
I 17,300 gp. Rocs only.
Fairly lucrative, but those suckers are fast. Not great for magic items.
F 13,000 gp. Vampires, medusae, and chimeras.
Low quantities of dangerous monsters with OK treasure. Pretty good for magic items.
D 7,300 gp. A grab bag. Hordes of humanoids and handfuls of powerful monsters.
I wouldn't fight a purple worm for this kind of dough.
B 4,000 gp. Ghouls, wights, nixies, hydras.
Going after a hydras does not seem worthwhile. One of the least magical treasures.
E 3,400 gp. Fairytale and mythic creatures, except for spectres.
Mostly in small numbers, except for the 30-300 elves. Elves are dirt poor compared to Men.
C 2,500 gp. Monsters of folklore and myth.
Gnomes are too poor to bother robbing. Pixies are poorer than nixes, just as land Men are poorer than water Men. Not great for magic items.