Yes it's probably cheaper to buy the 5 movie box-set + FF6 separately.
Yes it will be out of date when they release a 7-movie box-set.
Yes these films aren't going to challenge your mind for weeks after watching.
But for anyone interested in this particular set, this seems a decent price at £5 a film. Had several copies at the local HMV.(Worcester). I'm assuming it's nationwide.
At a quick glance, most of the online prices were between £39.99 and £44.99.
Edit: No idea if the picture is actually showing, but have uploaded to:http://i44.tinypic.com/28vw2ls.jpg