Methodology

GadgetGauge compares your listing against one price-evidence channel at a time. Channels are never merged or averaged:

• Private-party asking — active listing prices.
• Private-party completed — completed private-party sales.
• Dealer retail — dealer/retail pricing.
• Instant cash offer — trade-in/instant-offer pricing.
• Repair cost — cost of repairing a specific defect.

Every result shows exactly which channel it used. An active asking price is not proof of completed-sale value.

Each evidence record represents an exact commercial model at a reference storage tier, and — unless the record says otherwise — assumes: unlocked network status, good ordinary cosmetic condition, battery maximum capacity of at least 90%, no known functional defects, and no unresolved transaction evidence. GadgetGauge never adjusts for an attribute already represented in the baseline. Your confirmed answers only trigger an adjustment when they differ from that baseline.

Full precision is kept internally; the numbers you see are rounded to the nearest dollar, and offers land on the nearest $5.

comparison_midpoint =
  evidence_baseline
  + storage_adjustment
  + network_adjustment
  + cosmetic_adjustment
  + battery_adjustment
  + functional_issue_adjustments

maximum_offer =
  comparison_midpoint
  - unresolved_evidence_reserve
  - transaction_risk_reserve

opening_offer =
  maximum_offer
  - negotiation_margin (6% of comparison midpoint)

Demonstration adjustment hypotheses used today:

• Cosmetic condition: excellent +5%, good 0%, fair −10%, poor −22% of baseline.
• Network: unlocked 0%, confirmed carrier-locked −8%; unknown adds a reserve instead of a cut.
• Battery maximum capacity: 90–100% no change, 85–89% −3%, 80–84% −6%, 70–79% −12%, below 70% −18%; unknown adds a 4% reserve.
• Functional issues (each the larger of a fixed dollar floor or a percentage of baseline): cracked screen, back-glass damage, display problem, camera problem, charging problem, audio problem, and button problem. Face ID problem carries both a price deduction and a separate risk reason. Suspected liquid damage is a flat −25% plus a high-risk gate.
• Unresolved-evidence reserves: unknown battery 4%, unknown carrier status 5%, Parts and Service History unavailable or not checked 4%, requested screenshots not yet provided 3%.

These are editable demonstration hypotheses, not verified market claims — see data status below. A rule may explicitly supersede another so the same underlying problem — for example battery health — is never deducted twice. Ordinary cosmetic wear is handled by overall condition; a specific functional failure may apply in addition when it represents separate damage. If poor condition and multiple issues would otherwise drive the result below 15% of baseline, the numeric output is capped at that floor, confidence is lowered, and GadgetGauge tells you a specialist or parts-value review is required.

Risk gating runs independently of the price math and always wins. A cheap listing with an unresolved Activation Lock, a refusal to erase and activate, or an irreversible prepayment demand is not a good deal at any price.

Avoid — any of: the seller states Activation Lock will not be removed; the seller refuses erase-and-activate verification; the seller requires irreversible prepayment before inspection.

High risk — any of: suspected liquid damage; the seller refuses an in-person functional inspection; two or more serious functional failures (display, Face ID, camera, or charging) are confirmed; one serious functional failure plus a seller-cooperation warning.

Gather evidence — when no stronger gate applies and any of: the Activation Lock claim is unknown; erase-and-activate cooperation is unknown; carrier status is unknown; or two or more of battery health, carrier-lock evidence, Parts and Service History, and screenshot cooperation remain unknown or unavailable.

A great deal verdict can never appear when confidence is low or blocked, and never when critical security evidence is unresolved. Positive verdicts always remain conditional on completing every in-person check.

Confidence reflects both the completeness of your evidence and the quality of the underlying price evidence — high, medium, low, or blocked.

• High — evidence provenance supports real maintained market confidence, is recent enough, and no important unknowns or unresolved security/cooperation concerns remain.
• Medium — evidence is curated or moderately supported, with no more than one or two noncritical unknowns.
• Low — evidence is stale or sparse, multiple noncritical facts remain unknown, or your inputs materially depart from the available evidence.
• Blocked — critical security evidence is unresolved, a disqualifying seller-cooperation condition exists, or the engine cannot responsibly give price-forward guidance.

Curated demonstration evidence can never produce high confidence. That ceiling comes from where the data is from, not necessarily from the phone itself — see the demonstration data notice below.

GadgetGauge's price evidence today is curated demonstration evidence — not live market data. It is a fixed, reviewable, versioned set of illustrative U.S. private-party observations, not a live feed. Every result shows the evidence's observed date, its data snapshot ID, and the rule-set version that produced it, so you can tell exactly which numbers were used.

• It cannot authenticate or inspect the phone.
• It cannot verify ownership or stolen status.
• It cannot confirm a screenshot is current, unedited, or belongs to the listed phone.
• It cannot guarantee part authenticity.
• It cannot diagnose hidden or internal damage.
• It cannot validate the seller or guarantee meeting safety.
• It cannot guarantee the purchase will be successful.

GadgetGauge provides educational decision support — not an appraisal, offer, warranty, legal advice, or safety guarantee.