I'll start with the fact i don't really know on EE robes, never bought one as i've never found them to be useful and personally would say they're less than this, however based on people who do use them this is what i think they'd sell at to the right buyer.
https://ladderslasher.d2jsp.org/itemHistory.php?i=31584343&c=0 (EE) ~100-200
https://ladderslasher.d2jsp.org/itemHistory.php?i=1239020766&c=0 (EE) ~150-400
https://ladderslasher.d2jsp.org/itemHistory.php?i=27720223&c=0 (EE/Stat Hybrid) ~300-800
https://ladderslasher.d2jsp.org/itemHistory.php?i=7373999&c=0 (EE) ~200-500
For dex robes, the prices changes drastically for each point of dex, a level 55 with 38 or less dex is under 100 fg, at 45 dex you're at 3k+, at 48 you're already close to 6-8k+ and 50+ dex have bidwars well past the 12k mark.
As usual i'm posting what i think is correct.
https://ladderslasher.d2jsp.org/itemHistory.php?i=16116819&c=0 (Dex)
~700-1000
https://ladderslasher.d2jsp.org/itemHistory.php?i=7212997&c=0 (Dex)
~50
https://ladderslasher.d2jsp.org/itemHistory.php?i=628692&c=0 (Max Life Robe)
100-1000, depends on bidders. think the 500 paid is correct, personally would use a 15 dex with 0 life over it every day of the week, not sure who needs +500 life at level 1.
https://ladderslasher.d2jsp.org/itemHistory.php?i=11485927&c=0 (51 Dex Earth Charm)
1.8-2.2k
Angelic silksteel padded robe
Level Req: 45
Physical Defense: 0 to 34
Magical Defense: 25 to 63
+37 Dexterity
+16% Experience Gained
+2 Mana Regen
+1 to 2 Mana per Attack
Exp Gained hasnt been paid for in a long while, so even as a good side mod i dont think it really changes much. As a plain 37 dex robe its about 100, with the side mod maybe 200-300 imo.
Most likely to be wrong on that item.