I think it's important to remember that SE (at one time anyway) was big on customization. If everyone buys a pendant, then there is nothing "special" about those who have the associated in game item. I think SE prices (in addition to maximizing profit) may also take this into account and price the item higher so that those who do buy will have something more unique.
Basically I look at it as a way for people with the finances to buy gil to legitimately use their real money to customize their character. Most of the value of the in game item is in its rarity and looks not necessarily its effects, but we'll have to wait and see.
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First Lieutenant Kaminat @ Kujata
Wings of Honor
BRD 75 (Mordant Rime)
BST 75 (Primal Rend)
WHM 75 (Mystic Boon)
PUP 75 (Stringing Pummel)
RDM 75 (Death Blossom)
SCH 75 (Omniscience)
COR 75 (Leaden Salute)
DNC 75 (Pyrrhic Kleos)
BLM 75 (Vidohunir)
BLU 75 (Expiacion)
Currently leveling: NIN/BST
Nyzul Isle - Floor 100 = Clear
Subs: SMN 56 NIN 37 WAR 37 DRK 37 RNG 37
DNC 37 SAM 37 THF 37
Fishing 96.2 - Woodworking 74.0
Cooking 60.0 - Alchemy 56.2 - Goldsmithing 36.4