If a business charges for its parking lot access, does someone with a disabled parking placard have to pay?

If a business charges all individuals (including those without disabilities) for parking lot access, then yes, the business owner can charge people with disabilities for parking access. What would be a violation of the ADA would be to charge people with disabilities more for the same service than what individuals without disabilities are charged for the same service or privilege. The ADA Standards for Accessible Design apply to the parking lot, so the required number of accessible parking spaces must be provided in the lot. While some states and/or municipalities have enacted legislation that allows additional parking time in certain areas at a discounted rate for people with disabilities, this is not a requirement under the ADA.