Textract cost increasing

Hi all - what would cause Textract to suddenly move from $1.50 for 1000 pages to $5? AFAIK the customer hasn't changed anything, they're still scanning text only (no signatures, tables etc). They think Textract is repeatedly calling the GetDocumentTextDetection API but from what I have seen of the Textract pricing, it is all priced on number of queries/number of pages and API calls aren't charged? Haven't seen their CUR or anything like that as yet.