Will Prowse's favorite large panels are cheaper than that, including a 370w bifacial for $111 each in small quantities: https://signaturesolar.com/all-products/solar-panels/

Related video: https://www.youtube.com/watch?v=v33nbi7gKcY

Before you purchase anything try A1 solar. They often have deep discounts on single panels as well as container lots. For instance they have a 440 Watt panel priced at $140, six of which would get you 2,640 watts @ $840. https://a1solarstore.com/solar-panels/440-watt-solar-panels....

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!

Just wanted to clarify, are all these panels equal in size? Is there a "standard" solar panel format? It would be easy to otherwise get a much cheaper panel providing the same output if it was just a bit larger. It might be fine for ground installations but in your case space is at a premium