How much does a bathroom remodel cost?

This question cannot be answered, meaningfully without much more information. It is akin to asking "How much does a car cost"?
It depends on MANY factors such as: 1)the scope (i.e., what is included in the remodel, e.g., just replacement of fixtures? or all finishes demolished back to the framing?) or 2) the quality level = a toilet can cost $150 or $1000, etc) 3) the finish level = will the walls be ceramic tile or just drywall? and on and on.
One can get "bids" from different contractors, which is the best way to proceed. But beware, your ability to actually judge those different bids based merely on the bid price is not going to serve you well in the end. The contractor is more important a component than the "things" like toilets, tubs and sinks, and the quality and value of the contractor's contribution to the process can legitimately vary as widely as can the fixture costs.
Go back and hone your question for a more relevant, specific answer. Better yet, call the best contractor you can find in your area and let them educate you on the project while they are providing you a cost estimate for no charge!