It depends on your goal. Do you want to play nothing but classical music? Then it might take a while because you’ll have to learn to read well and spend a lot of time practicing scales, drills, and technique. Therefore, it’ll cost you more. On the other hand, if all you want to do is play some blues, pop music and accompaniments, then it shouldn’t take long. Thus, It’ll cost less. It also depends on your natural ability. Are you a fast learner? Do you like to take it slow and go at your own pace? All these need to take into consideration.
Another factor is where you live. Rate varies from city to city.