A 32 ounce bottle of the potion costs US$20 for those in the Continental US. At this time, the developer is not available outside this region. At 8 ounces a roll, this one stop solution costs only $5 per use and requires no special preparation other than warming in a warm water bath. Push and pull effects can be achieved with the developer. Increase the working temperature to 90 degrees for 1.5 stops push.
A quick review of the MSDS sheet for R3 Monobath shows that it is a solution of Kodak HC-110 developer combined with Rapid Fixer. HC-110 is reknowned for its long shelf life, so New55's claim of "Keeps for a long time" is probably true. Helpful if you only process a roll or two now and then. Convenience does sell, and it certainly sounds more convenient than mixing up the chemistry from powders!
If you have never done your own darkroom work, but would like to try processing film with this developer, simply fill a dish pan with warm water at about 85 degrees (measure with an inexpensive thermometer, guessing is difficult to get right). Wear nitrile or latex gloves when handling the developer. Place the developing olution into a smaller container (preferably a film developing tank, but not necessary), then measure the temperature until the solution is up to 80 degrees. Use enough water so that when the film tank is set in the pan, it is 3/4s submerged. The water should not be near the top of the film tank, as it may contaminate the developer solution. Add more warm water if the water in the pan gets cool, but keep the level below the top of the film tank. When ready, lights out, pull the film off the spool and carefully dunk into the film tank. A film spool helps to keep the film from touching itself, where the developer will not get a chance to work. Use an audio timer on your phone for timing, but do not use the phone for the first 2 minutes; the light from the screen will fog the film.