The first Oraclize query call coming from any Ethereum address is completely free of charge. Oraclize calls are free when used on testnets! This works for moderate usage in test environments only.

From the second call onward, you have to pay in ether for queries. While sending a query to Oraclize (that is, while making an internal transaction call), a fee is deducted by transferring ether from the calling contract to the Oraclize contract. The amount of ether to deduct depends on the data source and proof type.

Here is a table that shows the number of ether that is deducted while sending a query:

So if you are making an HTTP request and you want the TLSNotary proof too, then the calling contract must have an ether worth of $0.05; otherwise, an exception is thrown.