How to accurately price your mutable items -
First identify the item you have. The goal is to easily make fg without posting or reposting several times or adjusting prices! It is okay to slightly under price to ensure your item sells.
If we have a level 55 sword, rare quality, go to the market place,
Select type: Sword
Level range - 55-71
min magic level - MAGICAL
SEARCH
This will display all level 55 swords that are being sold.
Scroll down until you find rare swords for sale.
Magical Ulti Sword - 25 fg
Magical Ulti Sword - 25 fg
Magical Ulti Sword - 25 fg
Magical Ulti Sword - 25 fg
Magical Ulti Sword - 25 fg
Magical Ulti Sword - 27 fg
Magical Ulti Sword - 27 fg
Magical Ulti Sword - 27 fg
Rare Ulti Sword - 27 fg
Magical Ulti Sword - 27 fg
Magical Ulti Sword - 27 fg
Magical Ulti Sword - 30 fg
Magical Ulti Sword - 33 fg
Magical Ulti Sword - 35 fg
Rare Ulti Sword - 49 fg
Rare Ulti Sword - 49.98 fg
Rare Ulti Sword - 49.99 fg
Rare Ulti Sword - 50 fg
Rare Ulti Sword - 55 fg
Rare Ulti Sword - 56 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
Rare Ulti Sword - 60 fg
From this chart you can determine the median price is approximately 55 forum gold. You can also observe, someone posted a Rare quality weapon in the magical items. This will basically ensure you can buy that item and resell for a good profit !
Whatever the price range may be, if you can determine what a generally "real price" may be, this is your current resale value! You now have 2 options. You can go with the flow and sell for 48 fg to undercut the other people for a much quicker sale or you can go to 55-60 fg where everyone else posted and wait for a muter to eat them up.
For a more common practice, to determine the price of much more common items the practical application relies where you need to have the best price to sell your items. There is "hot items" and "cold items". Hot items always include; swords, daggers, focus heal, earth, fire, ice, plate mail, robe. Cold items always include; scale armors, clubs, axes, staff, lightning, wild heal, heal, wind.
When pricing muters for common items the best practice is to do a very general search. You can classify all items based on their lowest physical value and also in their hierarchy of importance of "hot items / cold items"!
For example; You have find a level 35 Mystical Club !
Type - LEAVE IT BLANK
Level Range - 35 - 35
Min Magic Level - Mystical
SEARCH
Mystical Drywood Staff - 8 fg
Mystical Admantium Axe - 9 fg
Mystical Drywood Club - 9 fg
Mystical Drywood Staff - 9 fg
Mystical Admantium Axe - 9.99 fg
Mystical Drywood Staff - 10 fg
Mystical Admantium Axe - 10 fg
Mystical Drywood Club - 10 fg
As you can observe, there "cold items" are listed together. It is best practice to match the lowest value 8 fg or go one value below to 7 fg to ensure your sale! This will work nearly 100% all of the time unless the market is inflated from someone massively buying items to transmute.
When searching for "hot items" but you cannot determine a price because there is so few or none, you can gauge a "hot item" price from the "cold item" prices by simply searching with the same parameters and finding anything available. Then use a little bit of sense and price under anything existing but certainly above the lower classified items.
This will work 95% of the time except for high level items that are extremely popular for muting. Then you just need to be aware of the market trends and it is okay to be off a few forum gold! If a level 55 rare sword is selling for 55 fg, a mystical should make 80-90 fg! An angelic sword should make 120-130 fg ! A mythical one should make 150-175 fg ! and so on.... Once you master and practice the market, your ability to determine such prices inherently grow!
Good luck and I hope this helps anyone!