I think selling each world at its own price, say £1 and then giving the players an option to buy all worlds up front for say £4 would have worked much better and not given such a backlash. I think paying for the game is fine, I just think it's too expensive given the platform, the audience and the competition on said platform.
Again, look at Rayman Fiesta Run. Completely free, tons to do, high quality, and Rayman, a known IP.