CHEAPENING CHALLENGER. After the 1986 space-shuttle disaster, Florida set up a foundation to commemorate the seven astronauts who died in the explosion and funded it with the sale of $15 special license tags. Now, 500,000 tags and some $10 million later, some legislators think the funds are being misused. They note that the commission's eleven-member staff has spent more than $600,000 on "administrative expenses," nearly as much as the design costs of a yet-to-be-constructed black granite memorial on Cape Canaveral. Some lawmakers have suggested a boycott of the license plates, and Representative Harry Goode is fashioning a bill to make the foundation accountable to state auditors.