Especially with a hard to control textual query interface I suppose that a huge number of requests will be burned through for finding the correct wording to mak

Especially with a hard to control textual query interface I suppose that a huge number of requests will be burned through for finding the correct wording to make Wolfram Alpha understand what you are trying to query. They should really make a free dev account which either operates on a limited set of data, or deliberately delivers wrong numbers in their results. A dev just needs a way to test his app without having to be careful about everyone of his tries costing real money.