Stop-Start Engine – Does it really save money in the long run?

Stop Start technology claims to save money and save fuel, but does it really?
Here are some calculation which work out if you save money over ten years with Stop-Start
Consumption figures come from this video
Daily cost of engine idling
0.63 litres per hour idling = around 80 Euro cents in gas. 80 cents for an hour of idling.
How long does an engine idle on an average 20 minute commute in a city? 5 minutes (25% of the journey time)?
So 6.6 cents each way, call it 20 cents a day**.
If you start an engine 6 times more with Stop-Start compared to a non Stop-Start engine, does the starter motor last 6 times less?
Assuming it does
Normal starter motor last what? 10 years? At a cost of 100 Euro.
Total cost of gas with non Stop-Start over 10 years = 20 cents * 365 days * 10 years = 730 Euro in idling, + 100 Euro for starter + 50 Euro fitting
GRAND TOTAL 880 Euro
With Stop Start 5 starter motors (because a starter came with the car) * 100 Euro * 250 Euro labour
Grand Total = 750 Euro
Stop Start Savings over ten years
Over ten years maybe a 130 Euro saving, about 13 Euro a year.
**And if we use 15 cents a day as the cost instead of 20 cents, a 25% reduction, the total without Stop-Start comes to
(15 cents * 365 days * 10 years) + 100 Euro starter + 50 Euro fitting
Grand Total = 697 Euro
Non stop start would be 53 Euro cheaper