Complex sentence: The size of the ships was limited by cost, consequent upon the limited budgets of the Countries placing the orders: their displacements were on the order of half that of contemporary ships being commissioned into the Royal Navy.
Split into simpler sentences: The size of the ships was limited by cost, consequent upon the limited budgets of the countries placing the orders. Their displacements were on the order of half that of contemporary ships being commissioned into the Royal Navy.