On the two tones and all gold models you can almost always get a discount.
It really depends on the dealer. I used to go to one place and you could get 10% off all steel Rolex models except Daytonas. You didn't even have to ask, they would have a price tag on them that reflected a 10% discount. Sadly, around 3 years ago they lost their Rolex account after more than 50 years as an AD for Rolex. Most ADs near me are big chains and they will not discount all steel models at all. I do hear of people getting discounts, but it really depends on the dealer (and some offer smaller discounts than they used to offer).
I wear my 15202 for everything, but I probably wouldn't wear it at the beach because it does not have a screw down crown. I know its WR to 50m, so it should be fine just for basic swimming, but I wouldn't wear something that costly in the water unless it had a screw down crown. I'm just super cautious with nice things...but others may feel more comfortable wearing theirs to swim in the ocean.
Such different watches...that its difficult to compare. ROs are luxury sports watches that are versatile enough to wear with a suit, but look great with jeans, a T shirt and leather jacket. The 1815, is purely a dress watch. The only Lange that I really love the looks of, are Lange 1s, so I've never seriously considered an 1815 up/down although their workman ship is fantastic. I think you have to consider whether you would wear a dress watch as often as a luxury sports watch...do you wear a suit and tie each day, do you attend a lot of dressy functions? If yes, the 1815 could be the right choice. I don't have to wear a suit and tie everyday and I don't attend too many dressy functions per year...but I am often still drawn to some dress watches...I just know they won't get worn all that often. Do you have a true dress watch? If you do not have a true dress watch, then that might be another reason to go with the Lange. That being said, I own a RO (15202) and its been one of the best watch purchases I've ever made. No regrets, no buyers remorse, its quality justifies its price...and it gets most of my wrist time. However, not knowing your work environment, if you have a very active lifestyle, and what watches you currently own its hard to give an opinion on how I would proceed if I were in your shoes.
Thanks for the response. I wear suit and tie everyday to work but don't otherwise attend many dressy events. My main watches are an IWC vintage series Inge and a GO pilots watch, as well as a Seamaster for weekend wear. That is to say, I don't have a dedicated dress watch but do have watches that I find suitable for most occasions.
I actually tend to think there is more overlap between the ALS and Audemar than you do. Surely the Lange is dressier but I don't view it as a pure dress watch. The arabics and subdials have some of the same design qualities as deck watches like a Portuguese, and avoid making he watch too austere.
On the royal oak front, it seems like only the ultra thin is a contender for folks who have chimed in but I feel like the 15400 is a more compelling alternative to the Lange because of its attractive price.