Goodwill Industries is not for profit. So the least you will save when shopping there is any state and local sales taxes. Here's Wikipedia's definition of them:
Goodwill Industries International Inc. is a nonprofit 501(c)(3) organization that provides job training, employment placement services, and other community-based programs for people who have disabilities. In addition, Goodwill Industries may hire veterans, individuals that lack education or job experience, or face employment challenges. Goodwill is funded by a massive network of retail thrift stores which operate as nonprofits as well. Goodwill's answer to its profit status is "As a unique hybrid called a social enterprise, we defy traditional distinctions. Instead of a single bottom line of profit, we hold ourselves accountable to a triple bottom line of people, planet, and performance."[3]
Goodwill operates as a network of 165 independent, community-based organizations in Venezuela, Brazil, Mexico, Panama, Uruguay, the United States, Canada and 8 other countries.[4] In 2011, Goodwills collectively earned more than $4 billion, and used 82 percent of that revenue to provide employment, training and support services to more than 4.2 million individuals.[5][6]
Any world-wide non-profit organization that boasts 82% of earnings going to support their mission, not outrageous salaries and expenses for executive, is okay in my book.