By Andy Silvester Cost, cost, cost: that will be the word of the day today. A tax cut will “cost” £5bn; a freeze will “cost” another £15bn. “Can Jeremy Hunt make the sums add up?” commentators will squeal. All of it is absurd, and not just because a tax cut doesn’t “cost” a thing: it simply means less money available for the Treasury to tip into an unproductive public sector, and more left in Brits’ pockets to spend boosting the economy. The sums involved in today’s budget, up or down a few billion, are rounding errors. The annual furore over the budget is as unserious as the theatricality of …