AWS AppSync cost increased after switching to Websockets

We had put off switching to Websockets as the old MQTT based subscriptions had been working without issues. However, given the 12/31/2021 deadline for the mandatory switch to Websockets, we went ahead and switched to the latest AppSync client in late December. Functionally, there haven't been any noticeable changes (negative or positive). However, the monthly cost has almost tripled. Our query/mutation/subscriptions counts are roughly in the same range as prior to the switch. Is there a reason we experienced this bump? Perhaps there's a way to track this down in the billing cost explorer?

Any help is much appreciated!