This happens with a lot of Champion skins - as skins get better in terms of quality, polish, effects, etc than older skins that were of equal or greater price seem like you're getting a bad deal. Mostly its just how it works; lots of us spent money on the very early skins that were literally just recolors, then Riot stopped doing recolor skins (and now they're doing 'Chromas')
And then there's the whole fiasco with legendary skins and annie...
Riot does periodically do "texture rebalances" or visual updates and when they do, they sometimes touch up the skins as well, but I wouldn't expect anything too drastic
