Why instead use a splitting by % for the best 5? ie. assuming the prize budget is 2000:

• 1: 30% = 600
• 2: 25% = 500
• 3: 20% = 400
• 4: 15% = 300
• 5: 10% = 200

Or there's any specific reason to provide 50% to the first and equally split the remaining along the remaining 4 (allocating 12.5% each)?