I guess I was being optimistic about 30 and 32 PPR encoders. All of those seem to be very expensive. 24 PPR is more typical - the Bourns PEC11R and PEC12R or example, which are under $2 at Digikey. They come with and without detents. But there are four transitions per pulse, so that would be 96 transitions per revolution if you counted each transition and had no detents. But really, the performance of something like that would be about the same as a pot, I would think. Neither would let you adjust easily to a specific setting.