On-demand bytes scanned and Editions slot-time.
The on-demand BigQuery compute charge: you pay for the bytes your queries read, not for time or rows. Because storage is columnar, the bill is driven by which columns you touch and how many partitions you scan — which is why two queries returning the same answer can differ in cost by two orders of magnitude.
Billed: Per tebibyte of data scanned, with the first tebibyte each month free. Billed on logical (uncompressed) bytes.