The issue is access. These watches are very hard to get (impossible without a huge spend relationship). Buying them on the secondary market for 3X retail, then hoping they go up even more is a dangerous game. They could keep going up to 4-6X retail, but at some point they stop increasing and someone is left holding the bag having paid 50K for a 15K watch, or whatever. I am still a buyer if I can use long held relationships to get a Patek/AP/Rolex/FP Journe at retail or close, but for myself, having made a staggering amount of money the last few years, I personally have pulled out of the secondary market pretty much completely. I believe these watches are tulips right now, or very very close.
edit: Now, if you want to "start" playing the game and try to get a couple Rolex at retail, then talk to @Doogles . My relationships go back many years so I think it is very hard sledding to come to the game now and make a dent, and if you are going to, a couple watches wont get it done. Id' say you need to be willing to spend 100K minimum to get on a radar to get any watch that is one of the really highly valued 2-3X retail pieces (Pepsi, Batman, Starbucks, etc). 100K is probably conservative. actually. To get a DJ and an Explorer II. Probably have to buy something else first then that is reasonable.