I have seen it sold for anywhere from 20 to 65 a medium square here this year.  I would buy enough to fill two 40 by 60 sheds 6 bales deep if I could buy it for 15 dollars a bale.  I figure I get about 3.5 to 4 bales and acre on average.

Here is the results from the last auction held here.
http://www.midamericanauctioninc.com/Pages/sales_results.html

The straw is typically sold per bale, not by the ton at this sale, unless the owner had them weighed.
As you can see good clean straw became extremely pricey this spring.  Many farms are grinding it in their feed rations, along with all the compost bedding packs, and a really wet spring, there was a very limited supply left here.