While there may be a number of factors that go into a hotel's "category level", one of the major factors is award use at that hotel. The more awards used, the higher the category will go. So even if the rate just doesn't seem like it justifies a particular level, if people keep using awards there, the category level will stay high.

Also note that some hotels may have big rate swings based on seasons, location, etc. Thus it may have very expensive rates for weekends or certain seasons (i.e. skiing, etc.) but be very in-expensive at other times. But Marriott really doesn't have a mechanism to change the category levels throughout the year. Thus it may look very out of whack for some nights/seasons, yet look like a bargain for other nights/seasons.