Wasabi used to be the cheaper option when B2 didn't offer variable free egress. B2 was basically "cheaper S3" as it still charged $0.005/GB for egress, while Wasabi was free egress (I think their upper limit used to be >1x your storage, so maybe that changed, or I'm misremembering?).

If your storage was fairly consistent, not tiny, and you intended to pull it regularly, Wasabi would come out on top. B2's egress change probably shifted the scales to favor B2 for those cases.