Fair point. I've stripped the 'filler' and updated the post to focus strictly on the raw math like that $1.077 Georgia tax feedback loop. Hopefully the technical data is more useful to the community than my initial draft.
Good call. It’s easy to let the writing get clinical when the math is this dry, but I hear you on the skim-ability. I’ve updated the post to lead with the actual findings rather than the 'important-sounding' filler.
I'm the builder. The motivation: lease math is technically disclosed on every
dealer document — MF is on page 3, fee breakdown is itemized — but it's not
in a format where you can act on it at signing.
A few things from these three deals that surprised me:
1. The Georgia TAVT has a feedback loop: each $1 of cash down reduces the
taxable depreciation base, which reduces the tax, which reduces NCC by ~$1.077,
not $1.00. Most calculators don't handle this.
2. The Louisiana dealer was $11 over the statutory doc fee cap. It's small
but it's illegal — and it's the kind of thing buried in a wall of line items.
3. The EV9 deal (Oregon) was actually clean — dealer at buy rate, $0 doc fee,
$0 add-ons. I wanted to include a "good deal" in the verification set because
if the tool only ever finds problems, that's its own bias.
The tool is at quotedefender.com — upload a screenshot of your lease quote and
it runs the same analysis. Happy to answer questions about the lease math or
any of the three specific deals.
I got frustrated by the wall of numbers at car dealerships and realized that standard lease calculators often miss the subtle, iterative math that dealers use to bake in profit. So, I built an engine to completely reverse-engineer dealer paperwork.
The core issue isn't necessarily that dealers lie; it's that they use complex, perfectly legal math (like marking up the Money Factor or capitalizing taxes differently by state) to obscure the true cost. To prove the model works, I spent the last few months running real dealer quotes—like a Mercedes GLC 300 in Louisiana (stream tax) vs. a Lexus TX 350 in Georgia (capitalized tax)—through the engine.
In every case, it back-calculates the exact Net Capitalized Cost, separates the interest rate markup from the captive lender's buy rate, and verifies the monthly payment to the exact cent.
I’ve detailed the math and methodology in the link, and you can run your own lease numbers through the live tool.
I’d love for this community to stress-test the app, poke holes in my tax logic, or let me know if I'm missing any obscure local fee structures. Happy to answer any questions about the reverse-engineering process or the state-by-state calculations!
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