Feature and price
Does the current menu support your query type? Does the price match the offer you intend to pay for? Confirm these two points before comparing package sizes.
Usage and validity
How are queries consumed and is there an expiry date? A low unit price may be less useful if much of the package goes unused. Compare actual terms rather than just a promotional headline.
Support contact
The fifth check is a clear support route within the service for payment questions. Keep the transaction confirmation if you pay. A query package is not a promise to find particular information.