For plugin support, please use a support ticket system. (I hardly check plugin's discussion forum)

This plugin allows a player to sell all items that are the same type as what he's holding, and in the chests which are in his faction claimed area (or just one chunk within the faction area.

You can specify whether you want to search all the chests in your all faction claimed area or just one faction chunk.

This was initially created to support Factions plugin but it also has one-chunk support for WorldGuard and GriefPrevention.
I can add support for other region protection plugins upon request.

Supported Region protection plugins: (use their name for "RegionType" option in the config.yml)

ASkyBlock,
BSkyBlock,
Factions,
FactionsUUID,
FEUDAL (since I don't have an access to this plugin, i haven't tested it but it should work.),
GriefPrevention,
Kingdoms+,
LegacyFactions,
NovaGuilds,
PlotMe,
PlotSquared,
Plotz,
PreciousStones,
RedProtect,
Residence (NOTE: as of Mar/2017, Residence depends on Kingdoms+ plugin),
Towny,
uSkyBlock
WorldGuard (ENTRY region flag) (6.x and 7.x)
WorldBorder,
...and more... this list is keep growing

Commands:

/siih | /siih help : displays the help menu
/siih reload : reloads the configuration file.
/sell chest : sell all items (same as the one you're holding or all items if you're not holding any) in your faction chests.
if this '/sell chest' does not work on your system, you can use '/siih sell' command instead.

Permission:

selliteminhand.use : allows you to use "/sell chest" or "/siih sell" command.
selliteminhand.reload : allows you to reload the config.yml

Dependencies:

EssentialsX,
Vault

Installation:
You just install SellItemInHand.jar into "plugins" folder.

Configuration:

config.yml

# +------------------------------------------------------------+ #
# SellItemInHand Configuration
# +------------------------------------------------------------+ #

# NOTE: Do NOT put tabs anywhere in the config!

Messages:
ErrorMsg : "&c[SIIH] : Some error occured."
SoldMsg : "&aSold for &c%cost% &a(%amount% %material% at $%worth% each)."
SoldAllMsg : "&aSold for &c%cost% &a(%amount% items)."
NoPermission: "&c[SIIH] : You don't have a permission to use this."
CannotSell : "&c[SIIH] : You cannot sell this item (%item%)."
SellStarted : "&c[SIIH] : Started searching chests... Please wait."
StillProcessing : "&c[SIIH] : Your sell request is still being processed."
CooldownMsg : "&a[SIIH] : You have to wait for &b%remaining% &aseconds."
NoAccess : "&c[SIIH] : You do not have an access to this area."

HelpMessages:
banner:
    msg: "=== &e[&aSellItemInHand Commands List (%version%)&e] &r==="
help:
    msg: "&a/siih help : displays this help menu."
reload:
    msg: "&a/siih reload : reloads config file."
    permission: "selliteminhand.reload"
debug:
    msg: "&a/siih debug <true|false> : turn on / off the debug mode."
    permission: "selliteminhand.debug"
chest:
    msg: "&a/sell chest : sells all the items (same type as one in your hand or all if you're not holding any) from all your chests."
    permission: "selliteminhand.use"

# adjust these event priority if those event processes from this plugin
# interfere with other plugins' event processes.
EventPriorityMap:
PlayerCommandPreprocessEvent: "LOW"

#
# you can nominate the type of regions, from which chests are searched
# Options:
RegionType: Factions

#
# if this option is true, only the location where you're standing for region check.
OnlyCurrentLocation: false

#
ThreadDelay: 2 # in ticks.

#
# cooldwon in seconds
Cooldown: 10

# supported Inventory type: CHEST, SHULKER_BOX
InventoryType:
- CHEST
- SHULKER_BOX

# if this option is true and ShopGUIPlus plugin is present
# this plugin will use ShopGUIPlus to find the unit price of an item.
ShopGUIPlus: false

SellItemInHand

Sell all the items (as same as you're holding or 'ALL') in the chest in your faction regions/chunks.