How much should it cost to hook up a dishwasher?

It is not too expensive. Did you have a dishwasher there before? If you did the connections should be there and ready. If not, you will need to find a place for it, usually under the counter, If you have a standard sink with a garbage disposal and standard piping coming out of the wall, a new stop valve with two connectors, one for the sink and one for the dishwasher, is required. if you have an older home with no room for the dishwasher under the counter, that could be the most expensive part.