Don't forget this is an 55mm f1.4 APO design. I think 4K is quite reasonable.
Yes it probably is, it's an advanced design with lots of large glass and very high precision requirements in mounting (to get the targeted resolution), this leads to big heavy and expensive. Other manufacturers could do a similar design with similar performance if they'd like to, but probably thought it would be too unpractical and expensive.
There's certainly a place for this type of lens line though I think, further narrowing the gap to medium format. While f/1.4 at this resolution seems a bit overkill for a manual focusing lens when it comes to all-around use, it will be great to have f/1.4 for accurate live view focusing when shooting landscapes from a stable tripod.
Someone who knows what the roadmap for this lens line is, what focal lengths will be next? 55mm is one of the "easier" ones to make, it would be most interesting to see what they can do with say a 24mm lens, or even better a 24mm tilt-shift
