It does unfortunately use plastic, but I was lucky enough to get a gallon of Dr. Bronner's liquid handsoap clearanced for 25 USD (regularly ~65 USD). To make foaming handsoap, I just mix somewhere between a 3:1 and 2:1 ratio of tap water to handsoap. (Foaming handsoap is just low-viscosity – and therefore highly diluted – liquid handsoap; the pump is what turns it into foam.)
It's been over a year, and despite using it both in my kitchen and bathroom, I'd say I've used less than 1/3 of it. The soap feels amazing, but I'd wager you could get a large jug of cheaper liquid handsoap with similar results.
Unfortunate that it uses plastic (and I think mine has palm oil, which really sucks; I didn't see it when I bought it), but it's still really good harm reduction over regular handsoap; for a few years' worth, I'm using less plastic than a gallon milk jug.