It's a Trap! Sort Of.
Not in the traditional sense, but the 8th-level Sor/Wiz spell sympathy [ench] (PH 292) is bait for a trap. Pick the kind of intelligent creature or pick an opposed alignment and lie in wait. Unlike most spells, the spell sympathy brings the adventure to the PCs, consequently--potentially!--enabling access to treasure without need for exploration, giving necromancers easy access to valuable corpses, and permitting contact with local fauna that could serve as allies if an unopposed alignment's chosen.
The ability to gather in one area actual creatures whose race or alignment the caster knows is more valuable than sending away the same. There are a huge variety of ways to kill or drive away creatures in Dungeons and Dragons, yet very few ways to force encounters. The spell sympathy permits the caster to do just that.
I'm speculating hard here, but I assume that was Gygax's concern with the spell originally, and why the spell sympathy (and its earlier iterations) has always had an expensive material component, a tradition Pathfinder continues.
Both Advanced Dungeons and Dragons and Dungeons and Dragons, 2nd Edition combined the 8th-level Sor/Wiz spell antipathy [ench] (PH 200) and the spell sympathy into the single spell antipathy/sympathy on page 89 of the Player's Handbook (1978) and antipathy-sympathy (1989) on page 238 of the Player's Handbook (1989), respectively. Both of the earlier spells' sympathy uses required 1,000 gp of crushed pearls and a drop of honey as material components, while the the antipathy uses were merely a lump of alum soaked in vinegar.
(Why the spell went from needing 1,000 gp of crushed pearls to 1,500 gp of crushed pearls is a mystery. Thinking it might be related to gem rarity in Dungeons and Dragons, 3rd Edition, I checked the Dungeon Master's Guide (2000) on Table 7-5: Gems (172), where the most valuable black pearl is worth an average of 500 gp and, at most, 800 gp. So that's not it. I'm unaware of an official explanation.)