Yup. I would essentially consider Prestige skins the most commonly made skin lines. You could basically say Prestige skins are collabs with other skin lines that come out ~once a month rather than once a year. Riot announces Prestige skins, excited about their new idea and how exclusive it is going to be. While I admit Riot never made a comment on the frequency of the release of Prestige skins, you would think they would be as frequent or less frequent than Mythic skins. Also, we have yet to see a Prestige skin for a previously made skin. If you want to have all Prestige skins produced, you have to play an obscene number of league games with less than a 2 week break in between. I have to play during finals/holiday/new years just to get Akali and I already know I will be away (I do know however that not every league player is in college/school, so this is just a personal endeavor)
All the Prestige skins are beautiful and well made, my complaint is the frequency of their release and cost (time & money)
Prestige KDA Kai'sa
Prestige KDA Akali
Prestige Blood Moon Aatrox
Also, all the prestige skins are for currently meta, op champions that needs nerfs. I think Kai'sa is somewhat balanced now, but Akali and Aatrox are in line for the chopping block.