Peat?

I am renovating my backyard and did what everybody said and had a soil test done. It is in fact as clayey as I thought and everything I see recommends amending by tilling in peat. From what I know, peat is very expensive at home depot, but honestly don't know where to get it in bulk and if that will be much cheaper. Doing a 6000 sq. ft. yard and the recommendation is at least 12 yds for that area. My question is if peat is really necessary considering the clay soil, and if I really have to do it, where do I get it cheap? I'm in the Minneapolis area.

I don't really want to use black dirt or topsoil because it compacts to easily.