I think economically it would be pretty difficult to justify 4-day county cricket whether or not Twenty20 was being paid (but note that I haven't lived in England for almost twenty years, and I don't really know the financial position of the game or any of the county clubs).

When Twenty20 was introduced a few years ago, I said several times here that, although I was not much interested in it, I could see it as a way of introducing people to cricket: it has worked at least in the case of my now thirteen year old nephew, who would never have concentrated even on a fifty over game when he was eight but was quite able to manage three hours or so. To the extent that Twenty20 works as an entry level form of the game, I supported it then and still support it now. However, what should have been an entry level "side-show" supporting the longer forms of the game is in danger of taking over and squeezing out the longer forms of the game altogether. The game does not need that, but the huge money which is being thrown around in the Twenty20 makes it inevitable, I think.

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Money won't buy you friends. But it gets you a better class of enemy.
Spike Milligan