while it's true that there's a retail markup, that markup is not close to a factor of 4. it's about 30%. the €0.12 per peak watt cost i mentioned for mainstream solar panels is not at the factory; that's a wholesale price in european markets, which are halfway around the world from the factory. if you went to the factory, you could probably get them for €0.10 per peak watt, about 45 dollars each for your 400-watt panels. (unless you don't look chinese, in which case trying to go to the factory might get you arrested, and you'd definitely have to buy more than 6–8)

the longer comment of mine i linked explains in more detail how you're getting swindled. in english!