I don't know the rates. You'd have to call them to find out. They may vary from center to center, depending on if they even want to do this for you.
Auto wrecking yards or crushers will also have scales if they do a lot of recycling. They need to be able to calculate the scrap weight for their rates to pay and this may be a better avenue than truck centers. Gravel quarries, etc. Lots of options.