The tuner says that this modification has practical benefits because it makes it easier to get to the back seats. Suicide doors were used a lot in cars from the horse-drawn carriage era, but nowadays they are not used as often. There are a few exceptions, like the Mazda RX-8, Opel Meriva, Toyota FJ Cruiser, BMW i3, and more recently the Fiat 500 3+1 (although only on the passenger side).
Mercedes G-Class by Mansory
There is no pricing info on the addition of rear-hinged doors to a G-Wagen, but if we are judging from the Mansory catalog, it likely will not be cheap. The same can be said for the pictured example's extravagant bodykit and reupholstered interior. All of those features can be combined with extensive performance upgrades to allow the G63's twin turbo 4.0 liter V8 engine produce a whopping 888 hp (662 kW / 900 PS).
Source: Mansory