Paracord is commonly rated at 550lb and is something like 7-10 cents a foot. If you want something beefier, static lines are have a much higher tensile strength but are about 10x as much.
You should understand the forces involved in rope use, you can easily generate forces 3-4x the weight of the object with small drops or shocks make sure 500lb is really what you are expecting to see with whatever you are doing. Climbing ropes are designed to reduce that shock (and the force) by stretching when loaded.