Not sure about the price change. It might change the game from being cheap and cheerful towards something people might think twice if it provides enough value for money.
From £10 for 3 credits to £20 for 3 credits is a large jump, I'm assuming most people go for this option instead of paying for a single credit. I don't play the majority of rounds these days, however if I do intend to play then I'll grab some credits as it seems like good value for money - but I certainly wouldn't bother if the price doubled.
For less than £20 I could buy from a wide variety of games on Steam which provide far more hours of entertainment than a web game which requires for you to get up in the middle of the night to stand a chance of competing.