They already had gold leaf before they contacted my old firm, problem was that it kept flaking off and did not look too good.
The cost was not an issue with that client, but I very much doubt it was cheaper.
The wall was a little over 20 square metres in area. We used custom made 200mm square blocks of glass reinforced carbon covered in a fleece like material with a brass handle, where the anode wire attached, as the 'brushes', and a carbon plate glued to the wall as the cathode connection. The electrolyte fluid carried the plating metal in suspension. The 'brushes' were dipped in trays filled with the electrolyte fluid and then the fluid was applied to the wall. It is a fairly slow process but works well enough. Interestingly, the gold fluid is actually blue before it is used.