As others have pointed out, the markup for smaller panels (really, anything less than the standard rooftop size) is extreme---more than an order of magnitude
I have sometimes wondered if it could be profitable for an operation to buy the standard-size panels in bulk, carefully saw them into smaller units, re-seal, and sell for $1/watt
It depends on the electrode structure I suppose. Presumably the market is too small, otherwise the panels would be cheaper to begin with. I still wonder what government pays for all of those small panels used by highway departments. Can one actually get a reasonable price (under $1/watt) if buying in bulk?