Well, on one hand, the money invested is to the largest part that of individuals installing PV on their own rooftop - and feed-in tariffs (see my reply to Jérôme) spread the costs to all German electricity consumers, without state mediation (no federal subsidy). (BTW, the largest photovoltaic solar power plant currently under construction, one in Bavaria, is just 10 MW.)

On the other hand, the difference in solar conditions is not as big as commonly assumed: the Sun's angle changes through the day and due to seasons on both places, the solar panel can be aligned for the best angle at the given latitude*; so only weather and higher atmospheric absorption at lower angles remains. Note: even under a clouded sky, absorbing diffuse light, modern solar cells achieve some 20-40% of peak power. From a very good place in India (2000 kWh/year with 1 kW) to a bad one in Northern Germany (800 kWh/year with 1 kW), there is only a 60% reduction.

Now, since import of electricity from distant areas like North Africa would entail significant losses, in the end the reduction of German CO2 emissions is possibly better done at home (Euro for Euro).

* To put it another way: one downsize doesn't come Euro for Euro, but in the form of used-up land area. At high latitudes, solar panels have to be erected at steep angles, demanding larger distances between rows of solar panels along the north-south axis. Of course, for rooftop installations, this doesn't hold.

_{*Lunatic*, n.
One whose delusions are out of fashion.}