Begin with conservative net resale proceeds
The calculation needs what you expect to keep, not a seller’s asking price and not an optimistic gross resale estimate. Begin with supported expected resale proceeds, then subtract marketplace fees, outbound shipping, packaging, risk reserve, and other selling costs.
If you do not have permitted, relevant evidence for resale proceeds, stop. The offer formula cannot create evidence. It only determines what a supported resale case would allow you to pay.
Define both constraints
The profit constraint asks how much you can invest while retaining a required number of dollars. The ROI constraint asks how much you can invest while retaining a required return relative to that investment.
Both matter. A cheap card can clear a high ROI while producing too little profit for the work. An expensive card can clear a dollar-profit target while tying up too much money for the return produced.
- Profit-limited acquisition = conservative net proceeds − required profit.
- ROI-limited acquisition = conservative net proceeds ÷ (1 + required ROI).
- Use the smaller permitted acquisition amount.
- Then remove acquisition shipping and buyer-side tax to obtain the maximum item offer.
Account for tax and acquisition shipping correctly
Your item offer is not always your total acquisition. Listing shipping is usually added after the item price, and buyer-side sales tax may apply to both. A maximum delivered acquisition amount must be converted back into a maximum item offer.
Card Scout subtracts acquisition shipping and divides the remaining amount by one plus the estimated tax rate. Negative results floor at zero because no non-negative item offer can satisfy the assumptions.
Keep the opening offer separate from the maximum
The maximum is an objective boundary for the assumptions you entered. The opening offer is a negotiation choice. Listing age and negotiation style can influence where you begin, but they should not increase what the economics allow you to pay.
A practical workflow is to choose a reasonable opening below the maximum, decide what increments you will accept, and stop when the counteroffer exceeds your ceiling. Recalculating the ceiling to justify a purchase defeats the purpose.
Stress-test the inputs
Run a conservative case, a base case, and—only when evidence supports it—a stronger case. Reduce expected proceeds, increase selling costs, or raise the risk reserve to see which assumption controls the decision.
If a small change turns the offer from attractive to impossible, the margin of safety is thin. Treat that sensitivity as decision information rather than hiding it inside one headline number.