Here is what I have to say.
Most of us do not care for the 1350 champs. If I wanted Fiddle, I would have just bought him with IP, play a few games, and make it up. The 1350 champs don't really make you money. (If you do buy 1350 champs with RP when on sale, then sorry.) We want to see the 3150 and up champs. And not the crappier ones that nobody really uses. We (mostly) want fun champs.
To put this in a perspective involving money, if a 1350 champ goes on sale, most of us buy with IP and make it up. If a 6300 champ goes on sale, most buy with RP due to the fact that saving up 6300 and buying a champ takes a while, and you could've spent it on something better like runes or rune pages.
In shorten terms, 1350 - little to no money, 3150 and up - large to massive amounts of money.
You can almost apply what I just said for skins, with a small change