do you have a picture...if it is a sout american it is worth big....."pounds".
I have never seen one...there is a leucistic one in Brazil if I'm correct.
p.s. are you sure it isn't a lungfish from Africa?
Like it has been said not a sa lung, one of the african species doesnt look like an annectens either, nice looking fish id pay £100-£150. The hard part is finding a buy but his tank looks tiny