I pay $1000 for a running machine with at least one piece of equipment. My C had a fully functional sickle mower, working PTO and belt pulley, and decent rubber. My dad's B has a hyydraulic pump and front mounted blade.
The tractor, as you describe it, is worth roughly $2-300, depending on if the wheels are rusted or not. This is assuming the tin is straight enough to warrant paint. The plow is worth $150, the mower $200, I bought my cultivators for $75. If the tractor has hydraulics then add another $75. By the way, I am curious about a 2-bottom plow on a C - they were rated for 1 16" bottom, mounted on the tractor. A 2-bottom 12" might work in sand, but don't put it at my clay. Before you buy, make sure the motor can be spun over! Otherwise you're looking at a part tractor. With all the equipment, I'd go $600. Remember, you're looking at $300 in tires and tubes, assuming the rims are good.