I've seen these available from Berkshire Records for around $35.00 US.
I have also seen them available on individual CDs from CDConnection.

Definitely worth checking out.  I swear during the fourth movement of
the fifth symphony the timpani man becomes so excited and demonstrative
he yanks out his own heart and pounds away with that.

My only real disappointment with the set is with the third symphony.
Cluytens does not take a heroic approach.  In fact, it sounds laid back.
Last night, I listened again to the Steinberg\Pittsburgh recording of this
symphony and found myself hooting and hollering along as I always do.  I
have not heard Steinberg's BSO recording, but if it is any better than
that, I don't think my larynx(or wife and kids) could take it.

I saw Symphony 6 available at Berkshire Records once.

Thomas Heilman