Sometimes different manufacturers try producing as cheap as possible, but at the moment of selling, they prefer to earn as much as possible without thinking in others, only in their own interest. That doesn't speak very well for them! Anyway, thanks to Internet and freedom of speech, it's possible to learn a little about multiple production mechanisms and DIY (do it yourself) solar panels aren't an exception.
Make your analysis, and decide if the market price is fair or not. We are going to provide a web page where all the process is well explained although the basis is acquiring solar cells and to make an array of them for getting the desired voltage and current.
After that, it's recommended building or purchasing a circuit to protect the batteries in which the solar panel is connected. In other section of the web page, there are plans to make this.
Finally, once the battery is charged, there are two options for using the electricity: Alternate Current (AC) or Direct Current (DC). As the battery provides DC, there's no problem to power up a big quantity of devices, but with AC (the usual plug at home) you would need an inverter (also there are numerous options in the market).
That's a nice first step to develop your own renewable energy harvester at a reasonable price while learning some electronics!
Here is the source: build your own solar panel.