Tank cost is negative

[Olympic1]

I made .cfg for a tank for storing 50 BioCake, but starts with 0. When I choose the tank it shows the cost but when placed on the craft the cost goes negative.

PART
{
    name = BioCake_Tank
    module = Part
    author = Roboto

    mesh = model.mu
    scale = 0.1

    node_stack_top = 0.0, 7.72552, 0.0, 0.0, 1.0, 0.0
    node_stack_bottom = 0.0, -7.3, 0.0, 0.0, 1.0, 0.0
    node_attach = 5.01, 0.0, 0.0, 1.0, 0.0, 0.0, 1

    TechRequired = basicRocketry
    entryCost = 1600
    cost = 850
    category = Utility
    subcategory = 0
    title = BioCake Tank
    manufacturer = DuctTape Aerospace Renewables
    description = DTARs latest tank technology for holding and cooling BioCake in space.

    // attachment rules: stack, srfAttach, allowStack, allowSrfAttach, allowCollision
    attachRules = 1,1,1,1,0

    mass = 0.25
    dragModelType = default
    maximum_drag = 0.2
    minimum_drag = 0.3
    angularDrag = 2
    crashTolerance = 6
    breakingForce = 50
    breakingTorque = 50
    maxTemp = 2900

    RESOURCE
    {
        name = BioCake
        amount = 0.0
        maxAmount = 50.0
    }
}

Edited December 30, 2014 by Olympic1
Answered

[UmbralRaptor]

Part costs are subtractive for... reasons.

You'll have decide on a base cost for a part, add up all the costs for the resources it will carry, and then put the total in the .cfg.

(Yeah, this confuses me also)

[Olympic1]

Part costs are subtractive for... reasons.

You'll have decide on a base cost for a part, add up all the costs for the resources it will carry, and then put the total in the .cfg.

(Yeah, this confuses me also)

So I'll have to increase the cost by 50, because 50 BioCake costs 50

[UmbralRaptor]

So I'll have to increase the cost by 50, because 50 BioCake costs 50

Yep. 100 in the cfg, 100 in the VAB when full, 50 in the VAB when empty.

[Olympic1]

Yep. 100 in the cfg, 100 in the VAB when full, 50 in the VAB when empty.

It worked, thx