I would say that the fact is 'saving' is singular and 'savings' is plural. This dictates the verb that follows. You could say A saving of $20 is ... or Savings of $20 are ...
A basement bathroom can be built for about $15,200, Fred estimates. Of that, plumbing is the largest component. These prices are based on costs for a small bath measuring about 6 by 8 feet, with 8-foot ceilings. However, many basements are limited to a 7-foot ceiling. Another potential cost-saving location for a new bathroom is the attic.
Suite Addition. Building out to add a bedroom allows you maximum flexibility. Adding a 14-by-16-foot master suite, including bathroom, over a crawlspace costs an average of $103,844 as of 2014, according to Remodeling. 2013 report by CNN estimates the cost of a new master suite installed over the garage at $50,000 to $80,000, which is well below the national average cost of adding a master suite over a crawl space.