They been broke for a long time. It doesn't list the price properly. If you want to see the cost, you can examine the item instead:
H:263 M:692 V:120 T:54839094 E:38,668,291,167 > list iceberg
A viking mage tells you, "You can buy:"
Item # Item Name Info Number Price
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[ 1167389] an iceberg core ice storm [ 9998] 338
H:263 M:692 V:120 T:54839094 E:38,668,291,167 > exa iceberg
You examine an iceberg core sold by a viking mage.
[1167389] An iceberg core brand new 170 [9998]
You see nothing special.
An iceberg core is a spell component made of ice.
It weighs about 1 pound and occupies roughly 4 cubic inches.
It is in brand new condition.
An iceberg core has about 9998 uses left.
An iceberg core is used for: ice storm.
An iceberg core is a component used in creating magic.
An iceberg core will last well into the future.
H:263 M:692 V:120 T:54839094 E:38,668,291,167 > buy iceberg
A viking mage tells you, "That'll be 170 talens. Thank you!"
You now have an iceberg core (*1 charges).
H:263 M:692 V:129 T:54838924 E:38,668,291,167 > sell iceberg
A viking mage tells you, "Here is your 124 talens. Thank you!"
The shopkeeper now has an iceberg core.
The 'list' price seems to change when you buy or sell it, however the actual buy and sell price are constant.
I just reduced your purchase price by 20%, so it is now 20% cheaper than frobozz's shop. The viking mage also pays you 5 times as much as frobozz!
There is another odd problem:
H:263 M:692 V:91 T:54839336 E:38,668,292,426 > buy white-peb
A viking mage tells you, "That'll be 40 talens. Thank you!"
You now have a translucent white pebble (*1 charges).
H:263 M:692 V:91 T:54839296 E:38,668,292,426 > sell white-peb
A viking mage tells you, "Here is your 220 talens. Thank you!"
The shopkeeper now has a translucent white pebble.
Happened for white-pebble, but not for another comp I tried. I only have special rates for bags, so the same rule should apply for the pebble, as did for the eel-tail. Don't let me catch anyone exploiting the loophole!