Compare against purchases you would really make
A donor can lower your repair spending if its usable components replace parts you otherwise need to buy. List those components individually and use the replacement price in your current save. Quantity means the number you need and can recover, not every similar component you hope to use someday.
Confirm each row only when the part's condition, compatibility, and planned use are established. Leave uncertain parts unticked. Their entered value appears in the excluded total so you can see how much your decision depends on assumptions.
Give a part zero value if you already have a spare or would not otherwise buy it. Count a physical component once, even when several future jobs could use it. This prevents duplicate inventory credits from making an expensive donor appear cheap.
Read savings separately from cash income
Confirmed purchases avoided = the sum of replacement cost × quantity for confirmed rows. Net savings = confirmed purchases avoided − donor purchase − extra recovery costs. The donor purchase ceiling subtracts recovery costs and your minimum savings target from confirmed purchases avoided.
These savings are relative to buying those needed parts separately. They are not a sale price, job payout, or cash deposit. You still need enough currency to buy the donor now, and an uncertain future use is not the same as a current purchase avoided.
When a purchase ceiling is negative, no nonnegative donor price meets the target with the parts currently confirmed. Reinspect, reduce your assumptions, or buy the required replacement directly.
Worked example: exclude the tempting spare
The illustrative rows contain one needed part at ¥900 and two needed parts at ¥500 each, totaling ¥1,900. An uninspected ¥800 spare is listed but excluded. A ¥1,400 donor plus ¥100 recovery cost therefore saves ¥400 compared with those confirmed purchases.
With a ¥300 minimum savings target, the maximum donor purchase is ¥1,500. The ¥1,400 example sits ¥100 below that ceiling. Ticking the uninspected row without evidence would add ¥800 to the allowance without improving what you actually know.
The sample names and values are invented for this calculation. Add or remove rows to match your own device, and reset the example if you want to reproduce the arithmetic. The worksheet does not store your entries.
Use the total in a whole-device decision
The original calculator accepts one donor-value total when comparing a device's repair path with keeping it for parts. You can use the confirmed purchases-avoided total as an input when both tools describe the same device and planned uses.
The original calculator does not have a separate donor recovery-cost field. If recovery would require extra spending, subtract that spending from the donor-value input yourself and do not subtract it again elsewhere. Keep resale revenue and replacement savings separate when interpreting the result.
Source and compatibility limits
The official Steam page describes device repair and buying spare parts. Our worksheet adds a transparent purchase comparison; it does not verify which component fits a device, predict marketplace contents, or publish fixed part prices. Official description checked October 14, 2026.
Match the part details and condition in your own game before confirming a row. Older demo data and unverified marketplace estimates cannot replace that check.