B&H has the Pentax 645D for $3,999 now. Five years ago, the 645D debuted at $9,995 and has been a very well-reviewed medium format camera. It features a 40MP CCD sensor and a weather-sealed magnesium alloy body. It was replaced last year by the Pentax 645Z, which features a 51.4MP CMOS sensor and now retails for $8,095.
You can find the Pentax 645D here at B&H Photo.