SIAFUND is the recipient of 3.9% of all successful storage contract payouts using Sia.
https://siawiki.tech/wallet/siafund
Siafund is a separately traded cryptocurrency from Siacoin. Siafund is limited to 10000 units which are all in existence already.
As of today, April 22 2017, "Sia's parent company, Nebulous Inc., holds 8835 of these Siafunds."
The only places you can find Siafund to buy or sell currently are: #siafunds Slack channel or Bisq (fka: BitSquare).
Past prices are otherwise scattered across the internet on varies forum postings.
October 2016: 2-3 BTC | https://forum.bitsquare.io/t/siafund-questions/784
June 2016: 2.75 BTC | https://www.reddit.com/r/siacoin/comments/4o4dov/fun_fact_siafund_market_cap_is_188_million/
This post is established as a location for interested parties to learn past prices for comparison to the current price.
Please help the community know the market price of Siafund; hopefully one user occassionally will take a screenshot of the bisq (fka: BitSquare) order book.