Exceptional items

Naturally, there are some items that are exceptions to this rule. Elixirs, for
example, are extremely rare, and for the most part, you can name your price on
them. These prices may vary with time, but so far, they're pretty stable.
If you want to include more items, send me an email.

Seal of Star/Moon/Sun - Name your price, they will pay it. I've seen level 10
items with Seal of Star going for 300,000 gold, and level 18s going for close
to 8,000,000.

Elixir/Weapon - From what I've seen, these can go for anywhere between 225,000
and 250,000 gold. Naturally, you'll always see some in stalls for higher
prices, and that's why you'll see them in stalls at that price. Nobody wants
to pay 350,000 gold for a weapon elixir.

Elixir/Anything else - 30,000 to 80,000. Accessories, Protectors, Garments,
Shields, the whole bit. They're not nearly worth as much as a result of the
focus on increasing your damage.
http://www.gamefaqs.com/computer/doswin/file/930711/43300