It varies with every piece of furniture and the type of material you would like to upholster the furniture in. Contact an upholster to obtain a quote before you begin to have an item reupholstered.
Yes, one of the benefits of having an item reupholstered is that it gives you the flexibility to choose whatever fabric or material you desire for your item.
There are some good reasons to reupholster, you may have an item that has a good frame and is comfortable. Rather than sending this item to landfill you can have it reupholstered.
Depending on what material you choose it can often end up the same price as an imported piece of furniture. The benefit of having something reupholstered is that it can be better quality than buying a new cheap piece of furniture.