Aren't some "SKINS" just Chroma swaps already? If so, which ones?

Most of the old re-colored skins are extremely old, which is why the majority of them are in the legacy vault. They exist because back when Riot first started, it's one of the only way they can get money when the game was, and still is, free-to-play and they didn't have enough resources to make high quality skins we see today.

Most needs to be all for the prices their charging for a palette swap.