There is more than just the cost of the hard drive to add an internal hard drive to a Blu-ray player. I can't find fault with that premium considering the cost to develop firmware, internal connections and controller, and customer support for a more complicated product. Look at all the questions here regarding how to copy files to the hard drive and access various files in dozens of different formats.
I think LG will be lucky if being first with an internal hard drive results in a profitable addition to a product that is sold at a very small profit margin to begin with. Don't forget retailers have to make a profit as well. Pretty tough business selling Blu-ray players now if you ask me, isn't competition great? The price is reasonable for this player in my opinion and I expect the BD570 will result in greater profits after customer service cost but both are being sold at slim margins.