In the U.S., at least, the burgers have always been "all beef." They taste different than other burgers because their beef comes from old, lean dairy cows that are no longer "useful," then they add fat to make up for the leanness.

Mcdonald's has been raising prices over the last few years mostly just because they can (and for shareholders, of course). They recently stated they've noticed "consumer resistance," so they'll probably slow down price increases now.