GCS launched as an S3 competitor (with an S3 compatible API). So their pricing was basically copy pasted from S3.

From the start though they offered more expensive to run features (a consistent list api, 1GBit transfer per file vs 100mbit for S3 at the time, Glacier-like storage with instant retrieval).

I think this pricing jump is mostly pricing it at what it always should have been. Plus a bit of the now being so focused on enterprises that the list price means less and its all about "call sales for more information".

S3 has built most of those features since then though, without a price increase.