"Buy expensive shoes" might seem like counterintuitive advice when it comes to saving money. But it's a hack that many people swear by. That's because spending more can often be the smartest way to spend less.Those who have mastered the art of being frugal aren't focused on the price tag in the moment. They're looking at the bigger picture. Many will happily spend a whack of cash on bulk groceries, energy-efficient appliances, or designer boots.…