While both sides bore enormous sacrifices during the French and Indian War, the Colonists in North America were at greater risk. The British spent more money, but a higher percentage of Colonists fought in the war.
One of the major factors was the smaller population of the Colonies compared to Britain. With fewer soldiers available, every life lost was a greater cost to the Colonies, while the British could easily send for more men. The Colonists lost many of their working men, decreasing their ability to farm and build; the remainder had to take up the slack with little training or impetus.
Another factor was the wealth of the two groups; the British spent more but had a higher base of wealth and influence on which to draw, while the Colonists were still establishing their nation and had fewer accessible resources and money. The Colonists had their economy disrupted, causing setbacks in the national process.
Both sides were hit hard during the war, but the established nation of Britain was in a better position to absorb and weather the loss of men and money than the fledgling Colonies.