How much would it cost to convert a manual 1972 karmann ghia to an automatic?

Note: There was no full automatic for the Ghia, but they did have an Autostick which is kind of a hybrid. You basically left the shifter in the first position for city and the second position for highway, and there was also a seldom-used "low" for very steep hills or trailer towing starts. It had an automatic clutch which operated by itself the moment you placed your hand on the lever (no clutch pedal!), and a torque converter so you could stop with the car in gear. Pretty trick engineering for the day, but it's hard to find a mechanic who understands them nowadays.

For conversion you will ned the autostick transmission, torque converter, control solenoid, autostick pedal cluster, vaccum port on the carb, fluid tank, and the special autostick-only oil pump which is a dual pump for engine oil and Transmission Fluid. You should be able to purchase all the parts from someone who has converted from AS to manual, which is a more common conversion.

To find a doner vehicle would be best, like from a auto wrecking yard. This would give you everything you would need to swap over. If you have to pay someone to do this job it would be in your best interest to sell your vehicle then purchase another that was automatic from the factory.