The lens seems to be worth between high $200 to low $400 according to Australian Sold listings on Ebay (
http://www.ebay.com.au/sch/i.html?_s...H_Sold=1&rt=nc ). I have no idea what it would cost to clean but probably a minimum of $50-100, possibly much more. It would sell for peanuts if the fungus is left on the lens so you have little choice but to have it cleaned or accept the loss as it is. Either way you loose out, unfortunately.
You might be able to clean it yourself as it appears that the fungus is under the front element. I have no idea if it is easy to remove the front element on these lenses but that's what the Internet is for. Of course you would need to buy the tools to disassemble the lens, and you might even damage the lens in the process.
Either way, that's a nice example of lens fungus and can I suggest you get a few better macro shots of it as they look pretty good IMHO.