Twice as much as you think it will.

Consult with a designer or someone who can give you ballpark figures. There's no way anyone can give you an informed opinion based on one sentence.

http://www.remodeling.hw.net/cost-vs-value/2014/

Impossible to say depending on how much demo, upgrades and size. Consider somewhere in the range of 5-10,000 per bathroom or more.

that will depend on what materials you want to get, how big the space is and the labor. you probably won't really know the ballpark estimate until you actually sit down with a designer/contractor--and after that it is, as hayleydaniels suggested, safer to overestimate the cost than to underestimate