Maybe so, but Subs, Seadwellers, SMPs (and even Seawolfs) are name watches, as in a lot of people have heard of the companies Rolex, Omega and sometimes even Breitling. They carry a kind of status with them, while, sadly, Sinn and Doxa do not.
Rolex and Omega are also seen as fashionable watches, partly due to their name and partly due to their price-tag.
Personally, for me, even though it won't come into use in the capacity it is designed for, the attraction of the Sinn U1 or U2 is the submarine steel used, the hardened bezel, the oils used in the watch which will allow it to work upto around -40 degrees celsius etc The U2 also has a capsule which keeps moisture away. I'm not sure if these ones also have the liquid filled interior. Things like these just won't be repped properly, and is part of owning a Sinn U1/U2... at least for me. I'd save up for the genuine. Others may (and probably do) feel differently.
By the way, where can I get a slightly used SMP or Seawolf for under $1k? I may be interested once I can save up enough! Was the $850 for a quartz or automatic full size? Please let me know.