You don't have to be in Concierge to take advantage of the spa facilities. They have spa and massage facilities at the Grand Floridian and Disney Institute. Pretty much almost any of the deluxe resorts can accomodate you, as well.
As for cost, yes they are a bit high, but I have heard they are well worth it. Usually I am in such a state of go, go, go, I never stop long enough to indulge. But, one of these days I will!