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.
1 According to an annual construction cost survey by Remodeling Magazine, a mid-range remodel of a 5x7-foot bathroom averages $14,109-$18,864; for an upscale expansion of a 5x7 bathroom to 9x9-feet within the existing house footprint, costs run $46,865-$59,456. According to an annual construction cost survey by Remodeling Magazine, a mid-range remodel of a 5x7-foot bathroom averages $14,109-$18,864; for an upscale expansion of a 5x7 bathroom to 9x9-feet within the existing house footprint, costs run $46,865-$59,456.