My set has the mesh/foam over the driver (I bought it a few years ago). I'm not sure if they revised the model to no longer have that foam or if that was just a manufacturing error with the missing foam (I seem to remember reading about that member who got a set without the foam). I should note that I have somewhat of a sensitivity to that 3khz range. Too high or too low and I struggle to find things listenable. Not everyone is bothered by that, so YMMV.
As for Superlux, my only experience with them is the hd660 that I modded (meh overall), but that's a closed back.
As for the ZX1's price, I do think $60 is too much given the overall quality of build, fit, and sound. $40 would be more reasonable. Putting big grado pads on the kph30i is similar fit (oversized foam pads that are on ear), similar build, and better sound (warmer, less punchy, but also less offensive lower midrange) for about 2/3 the price. But, I'm not sure if that would be an upgrade or more of just a side grade from your Superlux.
One semi-open headphone that can be found around $50 is the AKG 240s. Rolled off bass but they have some really nice midrange and make vocals just sound great. But that lack of subbass doesn't make them great for all genres.
I haven't really experienced many open backs <$75 price range that I would consider to be complete winners. Most of my experience in the price bracket is closed backs. So sorry I'm not more help!