The final fact is Denmark / Germany / Spain have the most expensive electricity in Europe, part of the extra cost is taxes, but even without taxes, Germany electricity is more expensive than France. If Energiewende was that cost effective, then why isn't Germany cheaper than France ?
Firstly because France is largely nuclear, which has historically been very cheap on a large scale, so a comparison to France would be tough for many countries, and secondly because it's a long-term project. The fact that it's not as cheap now doesn't mean it will stay so. But you can't build new infrastructure on a whim. For example, PV module cost is steadily going down. So when they get, say, three times cheaper in the next two decades (UMG cells, packaging improvement, manufacturing improvement...), if people at that point in time suddenly start putting them onto their roofs like crazy without some infrastructure investments done now, what's going to happen? Something nasty, I'd bet.