I would assume the "steep price" is due to Mistrel delivering the Q75 along with a set of quality double-shot PBT keycaps, while the backlighting-compatible ones on the Royal Kludge RK84 are much thinner and include laser-etched secondary legends which are non-translucent and will wear off after some usage (On the Ducky One 2 SF, for instance, the secondary legends are also shine-through).
Otherwise I would agree with you that the Q75's feature set leaves something to be desired (no backlighting, no aluminium bezels, no flip-up feet, one keycap less than most other competitors in the 75 percent keyboard market such as the RK84 or Keychron K2). Still, the Q75 is not a bad board and will draw some interest from people who dislike the aforementioned keycaps on the RK84 or the horrible cheapos on the K2. One of the Q75's strenghts alongside the keycaps, foam dampening and the small footprint in my eyes is its implementation of eco-friendly replaceable AAA batteries.