Charging unit
Check whether different sections consume balance in the same way. The supplied pricing screenshot shows query counts but not the complete charging mechanism. A package name alone is insufficient.
Empty and repeated queries
Ask whether an empty result, invalid format or repeated submission is charged. Do not assume a repeat is free. Read the error response before deciding whether to send the query again.
Validity and balance
Check whether a package expires and where remaining usage is shown. These conditions may matter more than unit price. This guide does not invent them; confirm them immediately before buying.