6300 IP
How many games do you need to play to farm up enough to buy one champion? The answer is: Way too many.
I think the way pricing works needs to be completely redone. Why would one champion cost 450 and another cost 6300? It almost implies that the more expensive champion must be "better" than the cheaper one.
I suggest that all the champions should have an equal but variable cost. The variation will depond on how many champions you already own.
For example, if you own zero champions, your first champion would cost for example 450, regarles of which one you buy. But then your second champion will cost maybe 600, again it doesn't matter which one. It only matters that you already own one, so the second one cost the next increment in price. And so on.
With this way it would be easier for new players to get going, and the cost would ramp up as you gain more experience and want to exand your champion pool, while at the same time not pigeon-holing you into only buying the cheap ones that you might not want to play, but feel forced to play because that's all you can afford.
on a first time league player.
I do agree 6300 is a lot, but I wouldn't implement a scaling IP system like you mentioned.
would be 450 and
would be 6300.