well, how long did you work on it. How many collateral solutions did you develop trying to solve the design challenge. That's what the logo is worth. Sure a logo like Sony's or Panasonic is easy to reproduce, but how long did it take, how many solutions did a designer attempt before they settled on that very simple solution. Get paid for the work you do.
erm..if that design looks good in black and white..I think the logo should be charge around USD50-USD200 but if too much gradient there and not so good to for print..I think that's would be a rejected logo..
I wont be making that exact logo into the black and white version like live-cms_com said it wouldnt work. I will make a two colour version no gradient, just keeping the shape and add a more modern version of chinese characters. The other the owner can use for promotional material like T-shirts or posters.
Personally I don't like it so it is of no value to me. If it was a "total match" to my concept and perception of my concept I'd pay $250.00.