This isn't the correct way of measuring.
You should be looking at the number of cycles.
The Phantom 2 Batteries was atrocious. $199 AUD for OEM intelligent batteries and 40 cycles before it puffed up. DJI promised 300 cycles but only gave 3 months warranty.
$200/40 cycles = $5 per 15minute flight. So an hour would cost you $20.
The P3 onwards had better discharge capabilities and firmware to prevent voltage sagging when the motors maxed out. The batteries were designed with better cell monitoring. Most users reported 100-200 cycles. You need to remember that each time you let self discharge from full to 50-60%, you are losing half a cycle. But losing that half cycle was better than binning your entire battery.
New price $999.00
Selling it after a year or 100 flights ($500.00)
Real cost $499.00
Cost per flight - 100 flights $4.99
Cost per minute - 20 minute flight $0.28
How about the guys that crashed there brand new drones in the first few minutes? MP at $1000, fly it for 5 minutes before destroying it. That's $200 per minute or $12,000 per hour of heart wrenching fun!