If you're being charged a different price for a plugin than what is currently advertised, it's likely because you're being charged the price that was set when you first subscribed to the plugin.
Currently, when you subscribe to a plugin, you're "locked in" at the price of the plugin when you subscribe. This means that the price you pay for the plugin will not change unless you cancel your subscription and resubscribe at a different price.
The rationale behind this is that if you subscribe to a plugin at $X/month, that's the price you will pay until you cancel it. This can sometimes work in your favor if the plugin price increases, as you will still be subscribed at the lower price.
However, if the price of the plugin has gone down and you would like to subscribe at the lower price, we recommend unsubscribing from the plugin and then resubscribing at the new price. This will also issue you a prorated refund for the remaining time you had when you were initially subscribed. The prorated refund will be reflected in your upcoming invoice for your app plan.
We understand that this may be an inconvenience, but it is the current system in place for plugin subscriptions. If you have any further questions or concerns, please don't hesitate to reach out to our support team for assistance.