Exact comparison is of course subjective, but I would prefer JW Blue over the cheapest of single malts, but I no-where near 10x as much. And, I would rather buy a £25 of Glenfiddich 12yo (picked because it is available, in my experience, in pretty much every supermarket and bar in the UK), even if the JW Blue was the same price.
So, good blended is more expensive than as-good single malt - indeed, it is also more expensive than great single malts. The only bottles I'll buy more than once are ones I personally consider great, and for me that's rarely less than £50 and never more than £500.
But, really, price isn't equatable to quality even within a category. You can't say that a £100 bottle will be twice as good as a £50 bottle, nor even that it will be better. The reason for spending more on a bottle is not that more expensive is better, just that, the wider your price range, the more options you have - and naturally, some of the more expensive bottles are better than some of the cheaper ones, and visa versa. If I couldn't afford it I could be perfectly happy with a lower top-end, and actually my second favourite bottle right now does cost around £50.
Two things to note: as with anything subjective, anyone can have a completely different opinion. Some people may genuinely love the JW Blue, enough to justify its cost. Most people who drink it don't, and they either haven't tried nicer whisky, or they are fooled by the price into deciding how good it is without paying attention to the drink itself, or (often) they don't really want to be whisky drinkers, and are doing it for the image not for the taste. But just because the majority are like that, doesn't mean there aren't people who, for their own tastes, are correct in loving it.
Also worth keeping in mind than JW Blue is notorious for being overpriced, don't think of it as representative of blended whisky. There are even nicer drinks in the JW range itself, and Blue is, at least by price, the top of their standard range. Green, for example, is considered by many to be nicer than Blue - not just better value, but nicer ignoring price. (I disagree on that, but at £30 it certainly is much, much better value.)
JW Blue is not whisky makers thinking "how can we make the best scotch", it is businessmen thinking "how can we market this", the drink itself is an afterthought.
edit: Personally I will always think single malts are much, much more attractive. But, blends can be good. JW, instead of trying to play with the blend to create an interesting and unique drink, tries hard to create a bland drink, with no interesting notes, a drink that will be acceptable rather than amazing to as many people as possible. It's not that they tried and failed, being smooth and boring is the purpose of the drink.
edit2: Am I just going on way too much about this?