Do you know what they put into commercial juice? Do you know the quality of fruit and veges they use? With a good quality juicer you can make your own juice which is healthier for you and cheaper.
The other benefit of having your own juicer is you can taylor your own juice. Like bananas in it? Just pop a bananas in with your mango and orange for your own creation. You can spend weeks tinkering with your juicer recipes to make the perfect juice just for you.