There are different grades of single malts and of blended whiskies.
Some single malts are not very nice, others are sublime.
Some blended whiskies are made of inferior whisky, the goal being to disguise a bad batch with some not so bad whisky. Other blended whiskies are a wonderful fusion of superior components with the ideal of achieving something that could not be achieved with a single malt.
In Jim Murray's Whisky Bible 2013, it is interesting to note that the highest ranked Scotch whisky of the year is a blend (Ballantine's 17 yo), but that the preponderance of high ranking whiskies are single malts.
Often older whiskies are more expensive (both blends and single malts), but there a lot of younger whiskies which are much nicer than older whiskies. Price is not always the best indicator of a good whisky.
Hope that helps!