Actually you don’t need to rely on the auto calculated value.
You can override it by adding the line:
value="17000" for example
It needs to be in the section anywhere after the id in your xml file for that item but before Itemcomponent like this:
FOR EXAMPLE:
<Item id="MYarrows01"
name="{=}My Arrows"
body_name="bo_capsule_arrow"
holster_body_name="bo_axe_short"
mesh="arrow_bl_g"
holster_mesh="arrow_bl_g_quiver"
holster_mesh_with_weapon="arrow_bl_g_quiver"
subtype="arrows"
flying_mesh="arrow_bl_flying"
weight="0.06"
difficulty="0"
appearance="1"
Type="Arrows"
value="17000"
item_holsters="quiver_back_top:quiver_back_top_2"
holster_position_shift="0,0,0.15"
is_merchandise="true">
<ItemComponent>
<Weapon weapon_class="Arrow"
stack_amount="50"
thrust_speed="0"
speed_rating="0"
physics_material="missile"
missile_speed="10"
weapon_length="97"
thrust_damage="90"
thrust_damage_type="Pierce"
item_usage="arrow_top"
passby_sound_code="event:/mission/combat/missile/passby"
rotation="0, -80, 25"
sticking_position="0,-0.97,0"
sticking_rotation="90,0,0"
center_of_mass="0,0.0,-0.13">
<WeaponFlags Consumable="true"
AmmoSticksWhenShot="true"
AmmoBreaksOnBounceBack="true" />
</Weapon>
</ItemComponent>
<Flags />
</Item>