2 ton/acre is an awful low yield.  But then again, if you are not going to apply fertilizer, that might be all you will get.

edit: BTW, we generally look at mowing and raking costs being on a "per acre' basis.  Why the "per ton" basis?  Also, are you looking at one cutting per year, or multiple cuttings per year?  (for alfalfa?) 

Care to elaborate?