If you are referring to Premiere Elements 12, there is no subscription purchasing plan for it that I have heard of. So, I am not sure where hans-g is coming from with the reply in post 1. This is not Premiere Pro. You need Premiere Elements answer.
With Premiere Elements 12, if you purchase from Adobe direct, there are two different prices, Upgrade one = if you own an earlier version of Premiere Elements and Full one = where you do not. Same thing, but different prices.
If you buy from other than Adobe, you pay one price at the time of purchase, whatever that authorized reseller is asking.
To your question
Is there also a mandatory annual license fee?
No. You buy Premiere Elements (one time purchase price) as per the Adobe Licensing Agreement. That is it.
There is no mandatory annual license fee associated with Premiere Elements.
Please let us know if that targets your question. Remember this is Premiere Elements and not Premiere CC (pro version).