Around query pricing, my understanding is BigQuery charges by bytes scanned uncompressed. Redshift Spectrum/Athena charges by bytes scanned compressed. That makes Athena/Spectrum cheaper as well.
It's not strictly true - depends on the rate.
The only thing you can say for sure - uncompressed analysis on Athena is too expensive
They have the same rate. BigQuery and Athena are $5/TB scanned. Unless you store everything in raw JSON text, Athena will be cheaper even with most basic compression.