My water comes from a private well and ultimately ends up in the drain field of my septic system and then presumably eventually makes it back down to the local table from whence it came. For me the cost of water is simply the cost of electricity for the well pump. I've never measured the power usage of the pump, but based on the voltage it runs at and the current rating of the circuit breaker on its circuit, and the rate it pumps water, and my electricity rates, the most it would cost to fill a large top loader is about $0.05, and so that is an upper bound on what a front loader could save me on water costs.

From what I've read the energy savings of a front loader comes from it drying better during the spin cycle, so you don't use as much energy when you use your dryer to dry the load. However, I usually do the wash in the morning, and then don't get around to moving it to the dryer until the evening. By then it has dried out quite a bit on its own, and is really just damp rather than wet. The dryer makes short work of it.

I'd have the same timing with a front loader, and so from the dryer's point of view the difference would be damp vs. less damp, not wet vs. less wet, so there would not be much energy savings.

I doubt that these tiny savings on water costs and dryer energy could make up the price difference over the lifetime of the unit.