No. 501(c)(3) charitible organizations are not required to offer services or products free or at cost. Nonetheless, providing such services or products at a substantial discount from their commercial rates can help persuade the IRS that your group is a real charitable organization with charitable intentions.
Many nonprofits support themselves partially by charging for services or products, but at a rate that does not completely cover their costs. Universities, therapeutic riding services, and symphony orchestras that charge for tickets are examples. Such organizations typically cover their funding gaps through various forms of fundraising.