Always read the fine print in advertising

In the following billboard, the price for a car rental is marked at 129.- Euros:

And as you can see, in the fine print, it says that at airports Sixt charges an extra 19%, i.e. 153,31 Euros in total. Why not you might ask – and I agree, why not. Let them charge what they want, where they want.

But I do ask, why they put up a billboard with this fine print copy AT THE AIRPORT? Yes, I took that picture at the airport in Hamburg!

Why did they not simply put up a billboard with the “real” price for that location?