Isn't that roughly half the cost of a bag in the hold?
In the last couple of years I've been very happy to pay £7 to put my cabin baggage in the hold. It will incentivise me to take a decent amount of clothing and footwear on holiday with me, I think. One suitcase in the hold for both of us instead of two small bags in the cabin.
How does the new charge compare with Ryanair?