MDF is MDF... theres no oak or birch MDF..at lowes cuz u have to buy it in oak or birch. they dont have a plain mdf.
Where the hell do you buy MDF?? By me it's at most $20 for a 4'x8' sheet. I wouldn't pay $35 either, but there seriously is a difference.
Then you really don't know where to look. Rockford can actually be pretty expensive compared to other brands that can perform the same as, if not better, than rockford. Not to say that rockford is bad, but there is alot more out there for the money.