In general you can do better than 10% on a Tudor (at least on the grey market), but you're not going to get a discount on a new model that's just hitting the dealers. Why would they give you a discount when there are people lined up to pay full price?
You can always try to negotiate, but they don't have much motivation to bend. Paying in cash or giving them a plausible reason to not charge you tax are your best bets. Otherwise, you'll need to wait until the watch is common enough to be just sitting in stores for people to walk up and buy.