It’s legit, they’ve been the biggest gray for years. Couple reasons. The biggest being that very few manufacturers actually sell at msrp in dealers. Yeah, Rolex does, some fancy minute repeater thing does, but uncle Suzy’s jewelry store on Main Street that has hamiltons would probably take 20% off for almost anyone who asked. Watch centric ADs maybe even more if they have slow moving models or some incentive to sell. Brands like TAG and Oris are both good brands imo, but tend to actually trade at 25 or 30% off. So anyway, this effect right here makes the pricing seem way, way off on the manufacturer website. In truth they’d probably rather not direct sale and instead sell wholesale to their dealers instead. The price likely reflects that fact for some brands.
and then the way jomashop gets watches. Generally it will just be overstock. Some jewelry store goes under or a model is over produced and some ad wants to dump their inventory for new bling, stuff like that. It’s also possible that these could be display models or returns, though I personally believe this is somewhat rare as you never really hear of people getting “used” looking Jomashop watches. They take returns like any other dealer if you’re not happy and generally have a good rep.
the only downside to a gray like Jomashop imo is that their stock is fluid. They won’t always have what you want. So, it may be that the variant or color you’re after just isn’t available at that healthy discount.