Originally Posted by Beaumains
IF they did this, it would have to be on the order of (at least) 10,000 IP = (no more than) 100 RP.
But what about the inverse? Would 100 RP trade into anything CLOSE to 10,000 IP? Even at 1,000 IP, that'd still be quite broken: just go buy a $5 Riot Points card to get more than enough for any champion. Or even if fixed, (so, say, 100 RP got you no more than 645, roughly where it'd be equal) that'd be still both troubling in how easily one could get runes for cash.
Also, think of low-tier champions: suddenly that 650 RP card, instead of getting you 2.5 bottom-price champions, could convert to IP and get you ~9.3 of them. Who'd ever want to buy that $5 "starter pack" then? You could just buy the skin normally, and still almost have enough to buy all the champions... So that'd be favorable even if just TWO of those four champs you didn't like. (which between Ashe, Garen, Ryze, Yi, and Annie, wouldn't be hard!)
Okay, then we cut it so that 100 RP gets you... 173 IP, so it's equal for the conversion rate for bottom-price champs. At that spot, what's the point? Just go buy a per-win IP boost. Spend 160 RP for a 2-win boost, win Summoner's Rift twice, and get a 100->181 conversion rate. That's what it boils down to for the "I want to buy IP" argument: just go ahead and buy yourself an IP boost. No, it's not instant gratification, but that's not what this game is about.
As for making RP from IP... To be honest, this game is free. There is no serious penalty for not paying cash: the cheap champions are just as liable to be overpowered as the expensive ones. And you certainly will spend a LOT of time playing this. Basically, you could compare this to a WoW or other MMO subscription: you'd have spent $120-180 a YEAR otherwise. So it's still vastly cheaper just to buy a little RP. Just go ahead and figure "well, this is part of my entertainment, so it deserves a bit of a budget."
You'd be surprised: in the end you'll wind up justifying the purchase of more RP than you would through any REMOTELY sane "convert IP to RP" procedure. (remember that rune pages are 590 RP vs. 6,300 IP, so THAT has to be the lowest conversion rate) Earning 6,300 IP is a pain; much easier to just occasionally drop $5 on an RP card. I know most playing have casual spending money that they could divert to that... And those genuinely destitute enough to not? Well, I'd hazard a guess that they aren't the ones doing the complaining, since they're the kind of people who're used to doing without.