Replacing a piston rod requires careful assessment and consideration of your specific machine and the extent of the damage. To provide an accurate estimate, I'll need to know the type of machine, the make and model, the rod size, and the location or accessibility of the rod (whether it's a through-rod, single-end rod, or double-end rod). In addition, the availability and cost of the piston rod or its components may vary based on your location.
Please provide me with the specific details of your machine and the piston rod you need to replace, and I'll do my best to give you a more accurate estimate of potential costs involved in the replacement process.