We don't yet offer "value based fees" on a consistent basis although it something we are considering. Value based fees reflect charging clients for what the work might actually be worth to the client, as opposed to the time it takes to do something, as most lawyers habitually do.
Top US consultant Alan Weiss has posted his own lawyer's memo offering his clients fixed charges. While Alan notes that isn't precisely "value based" it does mark a move in that direction, which as he says, is "ahead of the curve".
My own experience of trying to charge on a fixed price basis is that we, as the lawyers erring on the side of caution, tend to lose out. That isn't necessarily a bad thing especially for our clients, but it does mean that it needs fairly careful attention and to be kept constantly under review. Of course, if you were a client, you'd much rather that situation, than having the idea of the clock constantly driving costs upwards for every email read and phone call made. That said, all lawyers charges are matters of judgement, rather than simple mathematical calculations, and there should be a very strong element of "value" even in time based billing.

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