I just discovered (while renewing my fantastical annual subscription) that:
- if you renew an active annual subscription NOW,
- rather than letting it automatically renew later, on the day after it expires,
- apple refunds you for the unused part of your current subscription.
That meant, in my case, that I was able to renew my fantastical subscription at their current price before the price goes up in January.
I saved myself a few dollars by accident. Maybe you can too.