Methodology

Last updated: May 12, 2026

The Haus Report is built on a transparent, sourced valuation engine. Every number you see in a report can be traced back to a comparable sale, a public citation, or an explicit assumption you can edit in the Excel export. This page documents the engine end-to-end.

1. The Fair Value engine

Fair Value is the median sold price of comparable vehicles of the same variant, adjusted by up to twelve premium/discount modifiers. Each modifier is tied to a signal we extract from the listing and cited to an independent source.

Fair Value mid = Comparables Median × (1 + Market Δ) × (1 + Aggregate Modifier)

The low and high bounds are derived from the 25th and 75th percentiles of the comparable distribution, then adjusted by the same modifiers. The mid is the central estimate; the range communicates the inherent variance in a thinly-traded asset class.

2. Comparable selection (layers)

Comparables are drawn from the MonzaHaus market data corpus — aggregated from public auction platforms and classified marketplaces — using three concentric layers:

• Strict layer — same variant (e.g. 992 GT3), same body style, same drivetrain. Highest signal, smallest sample.
• Series layer — same generation (e.g. 992), any variant. Used when the strict layer has fewer than 5 comparables.
• Family layer — same model line (e.g. 911), any generation. Last-resort fallback for very rare cars; flagged in the report.

The layer used is disclosed on every report so the reader knows how concentrated the basis is.

3. The twelve modifiers

Each modifier captures a structural premium or discount the market consistently prices in. Individual modifiers are capped at ±15%; the aggregate is capped at ±35%. The caps prevent runaway estimates on cars with multiple positive (or negative) signals.

• Paint-to-Sample premium — rare special-order color, typically +10–15% per Hagerty market data.
• Complete service history — full documented service stamps; +3–6% per the PCA technical guidance.
• Low ownership count — single-owner cars trade at +3–8% over multi-owner equivalents.
• Original factory paint — no respray disclosed; +3–5% per Hagerty originality guidance.
• Documentation provided — window sticker, PPI, full books; +2–4% per Hagerty buyer-confidence data.
• Sold by Porsche specialist — Canepa, RPM, etc.; +2–4% reflecting curated provenance.
• Mileage delta — variance from the variant's median mileage; up to ±15%.
• Color rarity — non-standard hues; +1–5%.
• Transmission — manual on modern Porsches outperforms PDK; +5–10% on GT3 / Carrera S generations.
• Accident history — disclosed accidents discount by −5 to −12% depending on severity.
• Aftermarket modifications — non-OEM mods discount by −2 to −8% depending on reversibility.
• Title status — salvage or rebuilt titles discount by −25 to −40%.

4. Market intelligence dimensions (D1–D4)

Beyond Fair Value, four market dimensions provide context:

• D1 — Trajectory — 6-month and 12-month price trend for the variant, expressed as a percentage with direction.
• D2 — Cross-border arbitrage — price differentials across US, EU, UK and Japan markets, net of landed cost.
• D3 — Peer positioning — where this VIN sits within the variant's sold-price distribution (percentile).
• D4 — Confidence tier — composite of sample size, comparable freshness, and signal coverage. Reported as High / Medium / Low.

5. Data sources

Comparable sales and listings are aggregated from public auction platforms (Bring a Trailer, Cars & Bids, Collecting Cars) and classified marketplaces (AutoScout24, Elferspot). Modifier weights and rationale cite independent third-party publications including Hagerty Insider, Porsche Club of America (PCA) technical publications, and marque-specific specialist commentary.

We do not buy data from auction houses or accept compensation from marketplaces for featured placement. MonzaHaus is not affiliated with Porsche AG.

6. Refresh cadence

Comparable sales are ingested daily. The variant median, modifier weights, and confidence tiers are recomputed nightly. Live listing data on report pages refreshes every hour. Generated reports capture a point-in-time snapshot — the cover page records the generation timestamp.

7. What the report does NOT do

The Haus Report is informational. It does not constitute financial, legal, or tax advice. It does not predict your specific sale price — auction outcomes depend on bidder competition, condition disclosures, and timing factors the engine cannot model. It does not substitute for an in-person pre-purchase inspection by a qualified marque specialist.

Past performance — whether of an individual vehicle, model line, or the broader collector market — does not indicate future results.

8. Engine versioning & provenance

Every report carries an engine version (e.g. v3), a tier (tier_1–tier_3), and a content hash. The hash lets buyers and sellers verify the report has not been altered post-generation. Engine refinements are announced in the release notes and never silently change historical reports.

9. Feedback & corrections

If you spot a comparable sale we missed, a modifier weight that looks off, or a source citation that is broken, write to methodology@monzalab.com. We log every correction and credit contributors in the changelog.

© 2026 Monza Lab LLC. All rights reserved.