I know this is the type of thing that greatly varies with finishes, etc. But throw out some numbers for me for fun please.
My parents have a half bath on their main floor with a large closet next to it. They are hoping to combine these areas and get a shower in there. They will probably be able to keep the toilet in the existing locating, have to add a line for the shower, but will probably have to move the sink lines. Maybe be able to keep the sink line in the same place.
My parents are budget friendly peeps, so finishes will be kept basic. Basic tile, in stock vanities, basic shower fixtures, etc.