Ah i hadn't considered repair costs. It's still gonna take a very long time to recover the 18m odd from selling the 10% discounted hull as you'd only be getting an extra 5% saving each repair bill when you sell and rebuy. If you bought the full price ship then you'd be saving 15% each bill so you'd recover the costs in roughly a third of the time. Sounds great...
However I've just checked my stats and since i've started playing the game since launch i've spent 10m on repairs, dunno if that's low or high but if i saved 15% on that would be 1.5m. So to recover my 18-20m rebuy cost would take roughly 13 years, triple that if i'd sold the 10% discounted ship. So realistically there's no way i'd ever recover the costs though repair bills. If i planned on dying a lot then yeah i'd recover my costs via insurance claims at the 20m odd cost of each claim so that's 13 claims at 20m a pop... 260m So i'm out 260m but look on the bright side i've recovered my 18-20m sell and rebuy costs on the Cutter.....
I'd suggest CMDRs check their current repair bill stats to see if selling and rebuying makes any financial sense for them, you're gonna have to have outrageous repair costs to ever realistically recover the cost of rebuying the Cutter at a discount.