巨资 is news/business register — you'll see it in headlines about investment deals, blockbuster movie budgets, or stadium construction. Common collocations:
投入巨资 (tóurù jùzī, 'invest a huge sum'),
耗资巨资 (hàozī jùzī, 'spend a vast amount'),
斥资 (chìzī, 'expend funds').