Battery life is estimated as 1000 recharges before they deteriorate to 80 percent capacity. Say 100 per year for 10 years. I don't know the future cost of replacement batteries, but say £10,000 in 2021. So I am calling each use of the batteries as costing £10 per flight on which they are used. Not unreasonable.
Will a battery really last for 10 years, irrespective of the number of recharges?