Yes i think it is a fair price assuming good cosmetic condition. 400hrs is very low, and if it starts and runs well, no leaking or signs of obvious damage, it would seem like you are good to go. As a comparison there are a bunch of kubota BX with mowers and low hours starting to pop up around 7 grand, without loader....so your price sounds right given the tractor in question is a bit older, but a bit bigger - taller.
