McDonald’s is slashing its combo meal prices — despite weeks of tussling with restaurant operators who pleaded that rising costs have made it difficult to sustain deals already on the menu. Its US franchisees have agreed to keep the cost of eight popular combos 15% below the sum of the individual items’ prices, according to internal materials viewed by the Wall Street Journal. A combo meal currently selling for $10, for example, could go for as little as $8.50 under the new discounts...