~500$ for a 250/400W panel seems absurd, here in Italy you can buy a 500W solar panel for 100€ without effort or less. Given that you can buy a pallet of them, you can probably pay less than 100€ per 500W, I have found deals down to 77€ per 550W panel with pallets of 31 (31x550=+17k at 2405€), shipment included, and I'm talking about new half cell panels, not old stuff.