Wow, you missed the point hard. I guess I just assumed that people knew about galvanic cells... Okay, I'm sorry, let me backtrack.
The salt water has absolutely nothing at all to do with the operation of the lamp and it is not providing the electricity to operate the lamp. Salt and water are not used up or expended in the operation of the lamp. It's like the "lava" in a lava lamp. The lava isn't providing the power. It's decorative.
What is providing the power are two materials of different electronegativities, which we call a cathode and an anode. They are expended in the operation of the lamp. They are not free, are not available on remote islands, and are to be purchased - like any other batteries - from the supplier of the lamp.
Your response is exactly what the makers of this lamp are hoping for - people who don't know the science ending up believing that salt water powers this lamp, somehow. You have been deceived by their marketing.
EDIT: I responded to your one comment above without reading the rest of your comments in this thread. Had I done so, I would have been much less nice, as it is clear you are highly, highly ignorant and highly resistant to numerous people's attempts to educate you.