It really depends where. To give you an example, in San Francisco for a 1000-1400 sq.f. house it can be in the range of $30-$50 k per bedroom. But it might be nothing or it can be much more. There are many factors that impact house value. High quality bathroom has best chances to increase the house value, but you have to watch for "over improvement" for a specific area. Sorry for being so unspecific, but there are no general rules to answer your question.