For 15 years we have used the Alaska Air the mileage plan to purchase tickets to Europe through partner airlines. Any tickets offered with these plans require out-of-pocket fees plus miles. There is nothing new about this.
However, in recent years I have noticed vast differences between "partner" airline fees when using miles to book tickets. For example, we will be flying from Las Vegas to Frankfurt. For a business class, non-stop ticket, the "add-on" fee for Condor is $46 each way for each person. By comparison the British Air fee for a business class, one-stop ticket is $534 each way for each person. They both require 55-60K miles per leg. This means the total fee using BA for two people round trip would be $2,136 verses $84 Condor! We have seen similar differences when using American Airlines in recent years. BA is ways about ten times higher than their competitors.
We like to fly BA, and the Condor business class seats may be less posh than BA, but not this trip :)