I have found that a lot of buyers desire a bath tub in at least one bathroom in the house. Usually people want that to be in the bathroom that guests and children use. Sometimes they want a spa tub in the master suite and sometimes they mainly desire a spacious walk-in shower in the master bedroom. I can't really put a value on a bath tub or lack there of without knowning more details. It's just that some buyers will pass on a house without a bath tub so if it's possible to incorporate one, you might consider it.