LPG taxes are way lower and will stay that low until at least 2022. I´ve actually been able to get lpg for <0,5€ until 2016, even.
Normal gas ist at >1,5€/l and even Diesel is almost at 1,4€/l currently, completely crazy.
I have to thank our german government's incompetence for that. We got the highest prices in all of europe.....
For long distance trips with <130km/h at normal temperatures that would indeed be correct, but with my driving profile, namely ~12-15 miles one way twice a day and several longer autobahn trips/month with a lot of ~180+km/h parts efficiency quickly goes down the drain, especially in the 4 months where we have between -5 and 5°C.
People on this board have shown charts where the M3 consumes a whopping ~500wh/m in the cold months on the first ~10-15 miles..... So basically in the winter I´d almost exclusively be driving with 30+ kwh / 100km and that is before even factoring in the Autobahn.
With my driving profile 23kwh/100 km is actually rather optimistic