Been dealing luxury watches for a while now, and the #1 mistake I see beginners make is buying on vibes instead of numbers. Here's the actual framework:

1. Grey market spread

Every reference has a "grey market price" (what dealers actually trade it for, not retail). If you don't know this number cold for the pieces you're buying, you're gambling. This spread is where your margin lives.

2. Liquidity, not just price

A watch can be "cheap" and still be a bad buy if nobody's buying that reference right now. Steel sports models move fast. Weird limited editions can sit for months. Speed of resale = actual profit, since capital tied up is capital not working.

3. Full set premium

Box + papers + all links can swing value 10-20%+ depending on the reference. New dealers constantly underprice full sets or overpay for watch-only pieces because they don't track this gap by model.

The people making consistent money in this space aren't the ones with the best "eye" — they're the ones treating it like arbitrage with real numbers. Everything else (photos, negotiation, where to source) matters less if you get these three wrong.

Happy to answer questions if anyone's getting started.