Riot hard buffs Lux, she gets a prestige. Riot hard buffs Pyke, he gets a legendary.
But they totally don't buff champs to sell skins.
Edit- Just to be clear, they dont do this for all skins, mostly just the high Profile ones.
Take Zed and his legendary, he got nerfed on that patch yes, but it was a love tap Nerf, and was partially just a revert to the buff he record 4 patches earlier, which massively buffed Living Shadow's range.
Lux was steadily buffed to the point r/Lux was asking for nerfs, but didn't get those nerfs until a month after her Prestige skin.
Vayne got her Q cooldown reduction when ulting a patch before her prestige edition.
Pyke has just gotten a massive gold buff on his ult which coincides with forcing him back into the support role in a similar manner to Janna.
Even further, I don't think this is a bad business practice, skins are their income it makes sense to do this. Just don't pretend not to.
