The Royal Concertgebouw classifies seats in various categories in the seating plan of the Main Hall and the Recital Hall. There are several areas with a partially obstructed view (indicated in yellow on the seating plan). These seats are sold at a reduced price. This price is not always stated separately in the various schedules, but they can be found on the website for all concerts.
You can view the general seating charts for the Main Hall and the Recital Hall here:
Click here for The Concertgebouw's general floor plan. On this drawing you find the locations of the entrances, the wardrobes, the foyers, etc.